-Britain's royal palaces -- historic... -This amazing space is the grandest medieval hall in the world.

-...extravagant... -It's a magnificent fortress, but what it also is is the world's biggest jewelry box.

-...and jam-packed with secrets.

-Sandringham is the royal party palace.

They can do what they want there when they want, and the paparazzi can't photograph them.

♪♪ -In this series, we gain privileged access inside palace walls... -All plans suggested that if they could open this up, they might be able to reveal a long-lost secret.

-...and uncover the hidden treasures within.

-We're opening boxes to find jewels with handwritten notes from members of the family inside.

-We unearth the palace's dark secret histories... -Underneath this beautiful palace was a secret bubbling laboratory of horrors.

-...and we reveal the untold truth behind the palace's most dramatic modern moments.

-For Harry to be made a suspect for a criminal act is really, really serious.

[ Gunshots ] -I saw a gunman actually holding a gun and pointing it straight at the Queen.

-We kept it a secret, but it surprised a whole audience and, quite frankly, the world.

-This is the all-new...

This time we unearth a mysterious shooting on the Sandringham Estate... -The problem was no carcasses were ever discovered, so if they were shot, someone had very quickly cleared away the evidence.

-...reveal a royal near-death experience at Buckingham Palace... -This was the closest that Hitler got to actually killing the British royal family.

-...uncover the surprising makeup used in every Tudor palace... -There is a lovely recipe from the period which combines distilled honey with strong vinegar, milk, and, uh, the urine of a small boy.

-[ Laughing ] Okay.

-Explore the stories behind the Tower of London's most valuable treasures.

-No one else other than a king or a queen can turn up at a party with a great ball of gold.

-...and reveal how Windsor Castle became the center of one of the most haphazard weddings in royal history.

-Charles and Camilla probably just had their head in their hands and thought, "What else could go wrong?"

-Every palace offers something different for the royals.

Some a perfect backdrops for big public events.

Others provide the Windsors with a place for secluded respite, places like Sandringham House.

It's set in a vast 8,000-hectare estate and offers total privacy.

-It's remote.

It's discreet.

They can do what they want there when they want, and the paparazzi can't photograph them.

-But away from the house, there is one small portion of the estate the public can visit -- the Dersingham Bog National Nature Reserve.

-The Dersingham Nature Reserve is so special because it's a Site of Special Scientific Interest and it has a number of endangered birds, insects, wildlife that call it its home.

♪♪ -One evening in October 2007, three birdwatchers were about to witness one of Sandringham's greatest mysteries.

-Some ordinary members of the public and a park warden were strolling around, enjoying Dersingham, looking up at the sky, and admiring two beautiful birds of prey called hen harriers.

-The hen harrier is one of the most endangered birds in the country.

Back in 2007, there were just 20 breeding pairs in the whole of England, and Dersingham was one of the few places to see them in all their glory.

-And as the birds were kind of swooping in the air, suddenly, "Bam, bam, bam!"

Shots rang out, and one hen harrier plunged to the floor.

"Bam!"

again, and then another bird, the second bird, dropped to the floor.

-The witnesses observed that the shots had clearly come from within the private royal part of the Sandringham estate.

-Hen harriers are very protected, and killing hen harriers has a 6-month prison sentence and a huge fine.

-The following morning, local police searched the Sandringham estate for evidence, but the bodies of the birds were nowhere to be found.

-When Norfolk police contacted the big house to find out if anyone had been out shooting that evening, they said yes.

There had been one royal shooting party, just the one, and that comprised Prince Harry and one of his very good friends, William van Cutsem, and a Sandringham gamekeeper.

-He denied any knowledge of either shooting these birds or even seeing the birds.

-Prince Harry was questioned by the police, and the Crown Prosecution Service confirmed in a public statement that he was being considered as an official suspect in the Sandringham killings.

-That's incredibly shocking because for Harry to be questioned and be made a formal official suspect for a criminal act is really, really serious.

-Thankfully for Harry and his friends, the case was eventually dropped.

-The problem was no carcasses were ever discovered, so if they were shot, someone had very quickly cleared away the evidence.

-The CPS didn't have enough evidence to charge Harry, and so, to this day, no one knows who was responsible for the killing of those two birds.

-The case may remain the unsolved mystery of Sandringham Estate, but suspicion still lingers to this day over Harry's potential involvement, and it would have led to some awkward conversations back home.

-Let's remember that Prince Harry's grandmother, the Queen, was a patron of the RSPB.

-He would have been in big trouble with Granny and with the monarchy as an institution.

♪♪ -Britain's royal palaces are famed around the world, symbols of grandeur and unchanging tradition, embodied above all by royal HQ.

-Buckingham Palace sits at the heart of London.

-You know, it's what most people think about when they think about the British royal family -- is that famous building and that balcony scene.

-Buckingham Palace feels like an unchanging fixture of Britain.

But look closely and this building reveals a much more complicated history.

-Palaces aren't inevitable, and nor are they fixed entities.

They're always changing to suit the occupants.

-The entrance to the Queen's Gallery, with its classical style and stone columns, looks in keeping with the rest of the palace, but in fact it was only built in the 21st century, and it carries a hidden story.

It begins in 1940, at the height of the Blitz, when London was under attack from nightly air raids.

-This was every Londoner's nightmare.

This was death raining from the skies, and something like 20% of the city was destroyed.

-Hitler realized the propaganda value of the royal family to the British war effort, so the family and its palaces in London were particularly targeted.

-On the 13th of September, Hitler's targets hit home.

The palace suffered a direct hit from five German bombs when King George VI and Queen Elizabeth were at home in the palace.

-Apparently the Queen mother -- she then was Queen Elizabeth -- was removing an eyelash from her husband's eye when she heard what she described as the unmistakable "whir-whir" of a German bomber and then the scream of a bomb that set her knees a-trembling, she said, and then a huge plume of earth that rose out of the ground.

-They dived into the corridor and took cover, but if the windows had not been opened, the king and queen would have been very badly hurt.

This was the closest that Hitler got to actually killing the British royal family.

-The front gates and inner quadrangle were damaged, but one very private area of the palace took the worst of it.

-One of the saddest losses that day was one of the pavilions built by John Nash back in the 1820s, and that pavilion had been converted by Queen Victoria into the Royal Chapel, the place of worship for the royal family.

It was utterly destroyed.

The altar was smashed, and it was eventually demolished.

-It appeared a propaganda victory for Hitler, seemingly just the thing to sap British morale.

-The intention was to cower the British monarchy, but the effect of this destruction was to inject steel in the spine.

-Now Buckingham Palace had shared what thousands of East Londoners were facing, and the Queen mother herself said, "Now I can look the East End in the eye."

-The King and Queen, by their efforts in visiting the bombed-out sites, managed to bridge that gap between the upper classes and the working classes.

-At the end of the war, after nine bomb strikes, the palace was in need of urgent repairs.

But with the entire nation facing a new age of austerity, the royals decided to put off replacing the chapel.

It would fall to Elizabeth II and Prince Philip to decide what to do about the palace bomb site.

-The royal family could have chosen to simply reinstate a private chapel and kept it to themselves.

But the postwar years were a new age, and so Elizabeth and Philip decided to do something quite different.

They would build a new art gallery and present the Royal Collection to the nation.

-The gallery cost £45,000 and was the first part of the palace ever opened to the public.

-The queue of people on the opening day stretched to half a mile.

12,000 people saw it in the opening week, and they witnessed works by Leonardo, by Rembrandt, some of the greatest pieces from the Royal Collection.

The press described it as "breathtaking."

-In 2002, the gallery was enlarged and renovated for the Queen's Golden Jubilee.

-But in the early 21st century, this arrived -- a new monumental and permanent entrance into Buckingham Palace for all of us.

It drew on the example of John Nash and his lost pavilion.

It both looked back to tradition but also looked forward to the future.

-Coming up, a novel plot to steal from the Tower of London.

-A man called Thomas Blood and a bunch of accomplices tried to steal the crown jewels by sticking them down their trousers.

-Kate Williams models the Tudor Palace look.

-I think that could work for me.

I'm ready to be Henry VIII's mistress.

I'm all set.

-And Charles and Camilla's wedding-planning nightmares.

-The fact that the Queen wouldn't come just added to the impression that this was a completely cack-handed thing.

♪♪ -Britain's royal palaces are jam-packed with extraordinary treasures, and there is one palace that holds more priceless gems than any other -- the Tower of London, the royals' ultimate jewelry box.

The items stored here represent centuries of royal tradition, and the most prominent and significant of them all are the sovereign's orb and scepter.

-Nothing says royalty quite like an orb and scepter.

No one else other than a king or a queen can turn up at a party with a scepter and a great ball of gold.

-But these treasures are far more than simply a golden ball and a big sparkly stick.

-The scepter is nearly a meter-long golden rod, and it is encrusted with jewels.

There are 333 diamonds, 31 rubies, there are 15 emeralds, 6 spinels, and one large composite amethyst.

-At the top of the scepter is the great Star of Africa, the Cullinan, the first diamond.

It is absolutely stunning, and it is 530.2 carats in size.

-That's over 100 grams of pure diamond.

It tops a scepter made in 1661 for the coronation of Charles II, and though it might look like a sacred and unchangeable object, it's not.

The Cullinan diamond at its head was only added in 1910, nearly 250 years later.

-The Royal Family have a different approach to these sacred objects than the rest of us.

They are very happy to edit and change them.

-To the royal family, this is the chance for each monarch with these objects to put their own stamp on it, their own twist.

-It was King Edward VII who added the incredible Cullinan diamond to the royal scepter.

Originally dug up in South Africa, it was the largest diamond ever discovered.

-It's this incredible 3,106-carat rough, sort of like small ostrich egg.

It was an enormous piece of diamond.

-Unsurprisingly, the diamond attracted a lot of attention when it was sent over to London.

-It was under great pomp and circumstance.

It was sort of publicly known that this diamond was gonna be put on a paddle steamer with detectives and guards, but the reality was it was actually put through the postal service so that it remained utterly secure and unknown.

-After the diamond was popped in the post, the royal family was left with a problem.

A diamond that big is actually not very practical.

-The stone was then sent to the Netherlands to be cut down.

It was made into nine large stones and 97 smaller stones.

-The king then had the largest stone, Cullinan I, ingeniously added to his scepter.

-The scepter has a secret element to it, which is that the top frame is hinged so that that massive diamond, Cullinan I, can be taken out and used in other settings.

The most famous outing was probably at the opening of state parliament in 1911, where Queen Mary wore Cullinan I and II as a composite brooch.

She wore III as a pendant and IV at the base of her crown.

I mean, what an expression of wealth and power!

♪♪ -Today, the magnificent orb and scepter sit proudly on display in the Tower of London, but we're very lucky to still have them.

In 1671, Charles II was almost responsible for losing these priceless treasures.

-He decided to put them on public display in the Tower of London, where people could pay a fee to look at them.

One person wanted to do more than look.

-A man called Thomas Blood and a bunch of accomplices tried to steal the crown jewels from the Tower of London by sticking them down their trousers.

Thankfully, he didn't get away, and, thankfully, there is more security in the Tower of London today.

♪♪ -Diamonds and regalia are not the only tools available when it comes to creating the royal look, as this famous portrait in the Queen's House at Greenwich shows.

Queen Elizabeth I's Armada portrait is the most recognizable image of the Virgin Queen and takes pride of place in this historic royal building, but it hides a surprising truth.

-Queen Elizabeth I was actually about 55 years old when she sat for the portrait, but you could never tell.

She wears what's called the mask of youth.

-Sally Pointer is an expert in Tudor makeup and is here to reveal the secret palace ingredients behind the mask of youth.

-So, this is Elizabeth I's makeup box?

-These are recreations of the types of cosmetics Elizabeth would have used as part of her war against aging.

Are you going to try it?

-Let's try it.

-Absolutely.

So, cleansers -- you've got several choices.

There is a lovely recipe from the period which combines distilled honey with strong vinegar, milk, and, uh, the urine of a small boy.

-[ Laughing ] Okay.

-Maybe give that one a miss.

-After cleansing, Elizabeth was given her iconic white complexion, the face she wore to take on the palace court with a powder made from white lead.

-It's a very, very white powder on my finger, but when I put it onto my skin, it's actually not clown white.

-It's actually pretty magical.

It's rather fantastic.

-It is.

Lead is metallic pigment, so... -Perfect white... -reflects light.

-Aha.

-And we still use all sorts of light-reflecting pigments today.

-Light-reflecting makeups.

It's horribly toxic, isn't it?

-It is, and that's why I'm gonna take this off quite carefully.

So, I'm gonna mix you up a combination of a modern cosmetic powder with a little bit of fat.

Very moisturizing.

-It's disgusting.

[ Both chuckle ] Lead was toxic.

What was it doing to these women when they used it every day?

-It could make your gums recede and your breath stink.

It can affect your fertility.

-It can cause confusion.

-You're basically giving yourself lead poisoning.

-Absolutely, yes.

The sad thing is they knew it was poisonous.

We've known since the Roman period.

-It's really comparable to how we use some dodgy substances on our skin today, because we still want to look young and beautiful.

-Absolutely.

You think about the trade in fillers and Botox.

-So, we're so addicted to beauty, we're happy to sacrifice everything.

-And we have been doing so for at least 2,000 years.

-Fortunately, the finishing touch is something rather nicer -- a dusting of real pearl powder, a secret ingredient found in the Tudor Palace makeup boxes.

-It's much more subtle than I thought.

I really did imagine, to a degree, that it was a big blob of plaster-of-Paris-type makeup on their face.

But, really, what we have here is something that's much more light-reflecting, light-sensitive.

I think I could work for me.

I'm ready to be Henry VIII's mistress.

I'm all set.

-We need a little color in the cheeks and lips to finish up.

Okay.

So, we've got a choice between... little dried cochineal beetles... -I'm not sure about having beetles on my face.

-Okay.

How about some vermilion?

-Well, that's beautiful.

What an amazing color.

-Gorgeous color.

This is red mercuric sulfide.

-Oh.

Oh.

-It's mercury.

-So it's mercury.

-You'd struggle not to lick it off your lips if we put that on you, so out of the two... -I'll have the beetles.

-The Elizabethan look is to cover quite a bit of the cheek.

-That is quite bright.

-It's a different look, isn't it?

-A few more beetles mixed with some beeswax and alkanet root creates an iconic red lip, the final touch to Queen Elizabeth's unmistakable look.

-I definitely look different.

[ Scoffs ] I'm a bit torn on this look.

Aspects of it I really like, but was it really worth smearing yourself with urine, lead, lard, and crushed beetles?

-So, these ingredients have got an incredibly long history.

Modern-day cosmetics that are known to contain things like synthetic urea, carminic acid, which is the coloring principle in cochineal, refined animal fats -- these are all considered perfectly suitable for a modern-day monarch.

-Incredible.

Makeup is power.

♪♪ -We imagine royal palaces to be run like well-oiled machines, where events are expertly planned down to the finest detail.

But in 2004, Windsor Castle was at the center of a series of behind-the-scenes blunders that almost ruined the wedding of Charles and Camilla.

-For a long time.

Camilla was in a no man's land.

She went from this sort of weird position of being Charles's mistress to then being Charles's girlfriend in the shadow of Princess Diana, which must be an impossible position to be in.

-She was a royal girlfriend but had none of the rights of being a royal.

She wasn't allowed to sit next to Prince Charles at formal dinners.

She wasn't allowed royal protocol.

She wasn't an official royal wife.

-As time went on, it was clear that something needed to be done to formalize Camilla's position in the royal family.

-The royal family is very old-fashioned, and so for Charles and Camilla to do things together, for her to have the appropriate rank, she had to be married to him.

-Obviously, this is very dicey territory for the royal family.

The late Queen's uncle had to abdicate to marry a divorcee, the woman he loved.

And now, you know, a few decades later, we're talking about a future king marrying a divorcee.

-Charles finally got down on one knee for the good of Queen and country on New Year's Eve 2004, and the couple secretly planned to announce their engagement on Valentine's Day.

But the first of many PR debacles was just around the corner.

-Prince Harry got himself into huge trouble.

Sun newspaper got hold of explosive photographs showing him dressed as a Nazi.

Harry was going off the rails.

And then, of course, it called into question Charles's parenting.

Where was his dad?

Charles was really trying to repair his public image, so the last thing, frankly, he wanted was for his parenting, or lack of parenting, to come into scrutiny.

-Prince Charles must have been very aware that what Harry was doing was potentially very damaging to the royal family and to their image.

But, also, Prince Charles probably thought to himself, "Well, a royal wedding!

Everybody loves a royal wedding!

Let's completely distract from the Nazi uniforms and all those questionable pictures.

Let's say, 'Royal wedding,' and everybody will focus on that."

-But even this PR move was about to be taken out of the couple's hands.

-The news of their engagement was leaked to the Evening Standard, and that then bounced the palace into having to confirm that, yes, Charles and Camilla were going to get married.

When you are making such a big public announcement like that, you want to control the PR, you want to control the timing, and it very much took away from that kind of nice, careful planning that they had envisaged.

-Charles and Camilla were rushed into announcing that they would tie the knot at Windsor Castle, but little did they know this was just the first of a series of cock-ups that would jeopardize not just the wedding but the privacy of Windsor Castle forever.

♪♪ Coming up, things go from bad to worse for the happy couple... -If Windsor Castle has a marriage license, anybody could get married there, and that's not what Windsor Castle wanted at all.

-...a secret symbol of royal one-upmanship in Buckingham Palace Gardens... -For George, this was beautiful revenge to now show to the French who the victors really were.

-...and hidden royal torture at Kew.

-He had a terrible cataract, and they put a leech on his eyeball.

♪♪ -Britain's royal palaces have hosted centuries of historic events, and they don't always go to plan.

In 2005, Charles and Camilla announced their intention to marry.

The plan for the big day was to have a civil ceremony at Windsor Castle.

But they hadn't factored in one crucial detail.

-If they were going to have a civil ceremony and they wanted to have it at Windsor Castle, that would mean they would need to be granted a marriage license.

Now, if Windsor Castle has a marriage license, anybody could get married there.

I could get married there -- anybody at all -- and that's not what Windsor Castle wanted at all.

-If Windsor Castle had become a wedding venue, that would have been hilarious.

I mean, the bookings would have been off the scale.

Can you imagine the queues of people?

Every 15 minutes, everyone would be wanting another one, another.

"Oh, we got married in Windsor Castle.

Look at our pictures."

It would be like every Tom, Dick, and Harry being allowed to come in and get married in your front sitting room.

No.

-It's funny to the rest of us, but I'm sure there were some quite heated meetings afterwards about how on earth did we get to the stage that we almost open Windsor Castle up to being a wedding venue?

-This blunder meant a rapid alternative needed to be found.

It was announced that the nuptials would take place at the Guildhall on Windsor High Street, just up the road from the local branch of McDonald's.

But this caused yet another dilemma, this time for the Queen.

-The Queen felt, as the Supreme Governor of the Church of England, someone who supported church weddings, she felt that she couldn't go because it would just be not the done thing.

The Queen wouldn't, couldn't come to the Guildhall, I think, just added to the impression that this was a completely cack-handed thing and that it was doomed from the start.

-The Queen agreed to attend a religious blessing at Saint George's Chapel at Windsor Castle after the civil service in what the press deemed a humiliating snub to the increasingly less happy couple.

With less than a week to go until the big event, surely nothing else could go wrong.

But no -- six days before the wedding, Pope John Paul II passed away, and the day chosen for the funeral?

Of course -- it was Charles and Camilla's wedding day.

-Now, the Queen couldn't attend, so Prince Charles, next in line, had to attend this funeral on the Queen's behalf.

So that meant the wedding had to be pushed back to the Saturday, but it also meant that all the commemorative memorabilia -- you know, your teacups, your plates, your teapots and everything -- thousands upon thousands of them had the wrong date on them.

I mean, you just couldn't make it up at this point.

Charles and Camilla probably just had their head in their hands and thought, "What else could go wrong in the run-up to this wedding?"

-Broken but not defeated, the couple plowed on, but the strain on the usually composed bride was beginning to take its toll.

-Camilla even woke up on the day of the wedding with sinusitis.

She wasn't feeling well at all, and I think by that point, they were probably just like, "Whatever happens happens.

If we manage to get married and get through the day, it will be a miracle."

-Somehow, their prayers were answered.

The weather turned out well, and the couple entered the home straight.

Unfortunately, it was also the day of one of the Queen's favorite sporting events, the Grand National.

♪♪ -The Queen -- all she wanted to do was to watch the Grand National, and there was actually a side room at the reception that she'd had a television put in so she specifically could nip next door from the reception and watch the Grand National.

-But in her speech to Camilla and Prince Charles, she actually referenced some of the Grand National jumps, and at the end, she said, "My son is home and dry with the woman he loves."

-After clearing an unbelievable amount of hurdles, Charles and Camilla were, by all accounts, delighted to be finally joined together in matrimony.

-I think the whole thing was chaotic, but, you know, weddings are chaotic, aren't they?

The best ones are, anyway.

And so, in a way, it was the perfect British wedding because there was a bit of this and a bit of that and a bit of a muddle, but it was actually a great day.

-Britain's royal palaces take pride of place in some of the most picturesque and iconic locations in the country.

While some are tucked away in remote landscapes, others are surrounded by the hubbub of the city.

But even in the beating heart of the capital, there are still secret pockets of serenity to be found.

-Here in the middle of London, it's loud, it's frenetic.

The traffic is nonstop.

But just on the other side of that wall is a calm oasis of lawns and flowers and tended gardens.

It's the garden for Buckingham Palace.

-Buckingham Palace's Garden is the largest private garden in the capital, spreading over 39 acres.

It boasts over 1,000 trees, 325 wild plant species, and 30 species of breeding birds.

But first and foremost, it's the monarch's backyard.

-An Englishman's house is his castle, but his garden is his castle grounds.

And in the case of the royal family, that's literally true.

-If you wander the gardens today, you might spot one of the mulberry trees growing here.

But what most people don't know is that without the presence of this particular type of tree, there would be no garden and, in fact, no Buckingham Palace at all.

♪♪ -Buckingham Palace arrived at its site by accident -- a series of accidents, really.

The first of those was in 1608, when King James I decided he wanted a royal tapestry manufactory in England to rival the best in France.

-The royal courts of Europe in the 17th century were becoming hubs of fashion, and James I was quite put out by the fact that France was leading this.

Now, they had been planting mulberry bushes for decades to feed hungry silkworm larvae from which the threads extracted.

So James decided he had to get in on the act, and he ordered everybody to start planting mulberry trees.

-He planted four acres of mulberry trees where Buckingham Palace now stands.

The problem was the silkworms that feed on mulberries need white mulberries, whereas King James planted black, so the whole thing was a disaster.

-After this embarrassing miscalculation, the mulberry garden was parceled off and sold.

But King James's unsuccessful venture had a fortunate outcome for his successor.

-When George III came to the throne in 1760, he'd inherited a lot of old, sprawling palaces.

He needed something fit for a modern monarch, and the obvious place to buy, if he could, was Buckingham House.

It had been built at the turn of the 18th century by the Duke of Buckingham on the site of the old Mulberry Plantation.

A crucial portion of it was on Crown Estate and only leased, and it was difficulties in renewing that lease that allowed George III to jump in and buy the whole thing for £28,000.

He snapped it up at a bargain simply because of the refusal of silkworms to cooperate.

It was a failed mulberry-tree plantation that led to the existence of Buckingham Palace today.

-Thanks to George's canny business sense, the royals have enjoyed Buckingham Palace and its gardens ever since, and the jewel in today's gardens' crown is the famous Rose garden.

-Queen Elizabeth loved roses.

She always loved rose gardens, and the varieties are often very, very symbolic, so there'll be roses planted, either named after her or after family members.

And I suspect the late Queen has had more roses named after her than anybody else in history.

-Sitting in the middle of the Rose Garden is a slightly less subtle memorial, the Waterloo Vase, standing at 18 feet tall and weighing 40 tons.

-As the name suggests, the Waterloo Vase commemorates the famous British victory over Napoleon at the Battle of Waterloo in 1815.

The irony is, it was originally intended to commemorate a victory of Napoleon because he bought this great block of marble from Carrara in Italy.

But in 1812, when work began on it, Napoleon moved into Russia.

That was a disastrous campaign, followed up in 1815 with Waterloo and the British victory.

So the British got hold of this half-made monument, brought it over to London, gave it to the Prince Regent.

He got the sculptor Richard Westmacott to finish the carving, showing the Duke of Wellington as the victor and Napoleon as the vanquished.

-For George, this was a beautiful revenge, using this wonderful piece of marble that had been bought by the great Napoleon to now show to the French who the victors really were.

-The idea was that it would go into the Waterloo Room that George IV had built at Windsor Castle, only nobody calculated that it would more than likely crash through several floors if it was ever put into that room.

So it ended up in the Buckingham Palace Gardens, where Edward VII put it there and it remains to this day.

♪♪ -The royal palaces are some of Britain's most secure buildings, designed to protect the royal family at all cost.

-The Royal family are exceptionally safe within the Royal palace.

It's hard to get in.

It's hard to get out.

Certainly, the royal palaces are very, very well protected.

-But although they may be designed to keep the public out, they have also been used to keep the royals in.

♪♪ -We think of a king in his castle as all-powerful, but on the 29th of November, 1788, King George III was forced to move from his beloved Windsor Castle to Kew Palace.

The reason why they wanted him to move was because his mental health was deteriorating, and Kew Palace, in the middle of Kew Gardens, was chosen because it would be secret, and for the king, it was a prison.

Even as king, he couldn't escape the grisly treatments inflicted on those with mental illness at the time.

There were freezing-cold baths, forced fasting, and blistering.

There was cupping, where you put boiling hot cups on your skin to draw out the toxins, and lots of leeches.

None of these seemed to work, surprisingly.

And then along came Doctor Francis Willis, who had new and novel ideas about how to cure mental illness.

What he did, what he tried to do, was to reduce the king to a childlike state.

He used a straitjacket, a gag, a restraining chair.

On top of this, the king was not allowed to use cutlery and have solid food.

The king, the most powerful man in the country, is being bullied and coerced and reduced.

The king's suffering seemed to improve but then got worse and intensified by the fact that he went nearly blind.

In fact, he had a terrible cataract, and they put a leech on his eyeball to try and cure the cataract.

How awful.

The king finally died in 1820, really suffering very bad mental health.

Kew Palace, this beautiful palace in the midst of Kew Gardens -- it had been, for the King, a secret place of torture.

-Coming up, some unexpected residents at Buckingham Palace.

-She kept monkeys and an elephant and a zebra.

-And a palace uprising threatens civil war.

-Suddenly, Holyrood Palace became the nerve center of the Jacobite rebellion.

♪♪ -Britain's royal palaces are some of the most striking and extravagant buildings in the country, so it's only fitting that the royals come and go in style.

And the Royal Mews, hidden away at Buckingham Palace, houses everything needed for regal transportation, from gilded carriages to vintage cars and, of course, plenty of horsepower.

-If there's one thing that the British royals love, it's horses, and their love of everything equine is reflected in the grand royal processions that you see down the mall.

Of course you see the horses pulling the state carriages, and in those great military displays, you'll see many of the horses that come from the Royal Mews.

-As mere outbuildings go, the Royal Mews are exceptional.

They were built in around 1825 by John Nash at a cost of £65,000.

That's more than George III had paid to buy the property in the first place 60 years earlier.

Now, Nash transformed an existing riding school into the series of courtyards, a grand columned entranceway with a clock tower over the top, space for 100 horses.

This was like a town within the grounds of Buckingham Palace.

♪♪ -By the time Queen Victoria came to the throne, these stables employed around 200 staff, and, little known to the public, one curious Victorian ritual is still a daily occurrence.

-What most people don't realize is that post gets around all the royal palaces in London, even today, by using the horse-drawn Broughams -- you know, these wonderful carriages.

It is that important symbolic link with the past, that reminder of the glorious heritage that we enjoy in Britain today.

-Today the Mews houses and trains the Windsor Greys and Cleveland Bays that pull the royal carriages for state occasions.

But unbeknownst to their residents today, the Buckingham Palace stables have hosted some rather different and very unexpected four-legged friends.

-In the 18th century, Britain embarked on an imperial expansion, and so we had lots more access to new exotic beasts.

-One of the ways of showing your wealth and status in society was to acquire even more exotic animals as pets.

-Queen Charlotte was at the forefront of this fashion for exotic creatures.

In her gardens at Kew, she had free rein to amass rare plants and birds, but at Buckingham Palace, she created the greatest menagerie in the country.

-In the stables she kept monkeys and an elephant and a zebra, one of the true celebrities of 18th-century London.

-The zebra was so popular that the people of London were pretty much clambering at the gates to see this stripy horse, and George Stubbs, the painter famous for capturing images of the horses of the aristocracy, painted the zebra, really for those disappointed who couldn't get to see this animal.

-The zebra was the true focus of this menagerie.

It created such a furore that soon there was a satirical name given to it.

It was called the Queen's Ass.

-Despite its naughty nickname, Charlotte's zebra lived on royal grounds for another 11 years and became one of the most treasured animals in Britain.

♪♪ Whether it's by horse and carriage or flashy state cars, the royal palaces are perfectly designed for a grand entrance.

One of the best was at Holyrood Palace in Edinburgh, the monarch's official Scottish residence, when it welcomed a renowned 18th-century rebel.

-It's always important to enter a palace with style, and that was what happened on the 17th of September, 1745, when Charles Edward Stuart strode into Holyrood Palace in Edinburgh, all style, all glamour, greeted by 20,000 people cheering him on, shouting, "Long live the house of Stuart!"

He'd come to get Holyrood Palace back.

Charles Edward Stuart, known as "Bonnie Prince Charlie" because all of Edinburgh fell in love with him -- he was the grandson of James II of England and James VII of Scotland, who'd been deposed by his daughter and son-in-law, pushed out of the succession, and Charles Edward Stuart said, "I'm the rightful king.

I'm going to seize the throne."

It was an incredible moment.

Charles Edward Stuart had come to reoccupy Holyrood Palace.

It had been neglected for so many years, and Bonnie Prince Charlie was determined to return it to its former glory.

So, suddenly, Holyrood Palace became the nerve center of the Jacobite rebellion, thrumming with business and discussion as they planned their advance into England.

But this wonderful rebirth for Holyrood Palace -- it was only for six weeks.

Charles Edward Stuart and his army set out to fight for the throne, but, unfortunately, he wasn't the best commander and he and his army were forced to retreat.

He managed to escape the English clutches by fleeing to France dressed as Betty Burke, an Irish spinning maid.

It was a long way from being the glamorous, fantastic prince of Holyrood Palace.

♪♪ -Next time, we uncover the royal secrets of the Palace of Westminster... -This is the most important piece of furniture in the whole of the Palace of Westminster.

It's the sovereign's throne, and it's used by the monarch just once a year.

-...reveal Princess Diana's palace plot to impress her prince... -She said, "I want you to dance with me this Christmas as a surprise for my husband."

-...and meet the cannibal king of Saint James's Palace.

-Underneath this beautiful palace was a secret bubbling lab full of skulls.

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