What’s it like to live at Hogwarts? Just Wizard! Duke who transformed glorious Alnwick Castle gives the Mail a private tour of its blood-soaked secrets

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The Percy family of Alnwick Castle — that splendid, 150-room, heavily crenellated, many-towered magnificence perched on a rocky outcrop above the River Aln in Northumberland — have not, traditionally, lived long or quiet lives.

Over the past thousand years, the Barons, Earls and Dukes of Northumberland have rebelled against monarchs, battled relentlessly with Scots and shuttled in and out of the Tower of London on various charges of treason.

Some have been shot, others hung, drawn and quartered, and a few had their heads displayed on spikes in cities around the country after a disastrous uprising against Henry IV in 1403.

Time and again, Percys have popped up throughout history. The great Sir Henry ‘Hotspur’ Percy, who led endless rebellions against Henry IV of England and was slain at the Battle of Shrewsbury, was immortalised in Shakespeare’s Henry IV, Part I.

Jane Fryer meets Duke of Northumberland Ralph Percy, 62, at his home at Alnwick Castle (pictured), Alnwick, Northumberland

The 6th Earl was secretly engaged to Anne Boleyn before she became Henry VIII’s second wife, the 7th was beheaded, the 8th was shot dead in the Tower and the 9th was thought to be involved in the Guy Fawkes Gunpowder Plot and was incarcerated for 16 years.

Their sprawling home — now the second-largest privately inhabited castle after Windsor — bears the scars of centuries.

There are musket pockmarks, made by Oliver Cromwell’s army, in the yellow sandstone. A suit of armour hangs above one door. In the cone-shaped dungeon, the screams of doomed Scots are all too imaginable.

Oh, yes, and in the main entrance, a maroon board offers Broomstick Training sessions on the very spot where Daniel Radcliffe had his first flying lesson in Harry Potter And The Philosopher’s Stone.

The Duke and Duchess of Northumberland, Ralph and Jane Percy, pictured at their home, Alnwick Castle, in Northumberland

The latter is courtesy of Ralph Percy, the 12th Duke, who, with the help of his energetic Duchess, Jane, has transformed Alnwick into one of Britain’s most visited attractions. He has now written a book about the castle, which he will be discussing this week at the Chalke Valley History Festival in Wiltshire.

‘There are several times throughout history when the whole thing could have disappeared — when we’d rebelled against the crown or the money had run out,’ he says.

‘Or the castle had collapsed and there was the whole Catholic-Protestant problem that dominated the 16th and 17th centuries. Or there simply was no issue to take it on. But, somehow, the Percys managed to cling on.’

Ralph was an accidental duke himself, plugging a difficult gap in the Percy family history.

He was a second son, a passionate tennis player, a trained surveyor and was once known as the best shot in England.

Harry Potter and the Philosopher's Stone (2001) filmed at Alnwick Castle

He was happily married to Jane, a stockbroker’s daughter from Edinburgh, whom he’d met at a party when she was 16, and lived happily in a pretty Georgian farmhouse on the family estate with their four children and dogs.

Meanwhile, his brother Harry (Henry), the 11th Duke and the Queen’s godson, lived a racier — and ultimately tragic — London life of parties, girlfriends (he dated Naomi Campbell’s mother Valerie, American actress Barbara Carrera and model Jackie St Clair) and ambitions in the film world.

‘We were three and a half years apart and were very close,’ says Ralph. ‘He liked the castle, but he was a bit depressive, and I think he found the whole thing — living in this goldfish bowl and being responsible for so much — difficult.’

And then, in 1995, Harry died of an accidental amphetamine overdose and Ralph, who had been working on the Northumberland estate for two years, inherited the lot: title, Alnwick, Syon House in London, vast swathes of land in the north and south of the country, plus a £350 million fortune.

He, Jane, the kids and their dogs moved into the castle keep, and that was the end of their old life.

Today, the castle is exquisite — an assault of gilded ceilings, gold leaf, polished floors, gleaming swords and exquisite views over the Capability Brown-designed parkland.

There is a art collection, described as one of the finest outside the Royal Collection, which includes works by Turner, Titian, Canaletto, Van Dyck and William Dobson. Unusually for a castle, it is also warm, impeccably clean and smells of expensive scented candles.

TV drama Downton Abbey was filmed in the library of Alnwick Castle, Alnwick, Northumberland . (left to right) Alun Armstrong as Stowell, Allen Leech as Tom Branson, Matt Barber as Atticus, Lily James as Lady Rose, Michelle Dockery as Lady Mary Crawley, Laura Carmichael as Lady Edith, Matthew Goode as Henry Talbot, Harry Haddon-Patton as Bertie Pelham and Sebastian Dunn as Charlie Rodgers

At first, Ralph, now 62, and his family felt trapped. ‘It was quite difficult because, in the summer when the tourists are here, it’s hard to get in or out of the house through them. We found that weird, coming in and out with your dogs and tennis racquets,’ he says. ‘People did seem to stare.’

With the only private bit of garden 100 yards from the house, the children mostly stayed inside rather than brave the crowds; and the dogs couldn’t be let out for fear of messing up the lawns.

Meanwhile, he and Jane worried that wealth would spoil their children and went to the High Court to have their heir George’s £250,000 annual income delayed by seven years until he was 25. They also insisted their children learn to cook and earn their own living.

Now they decant to Scotland for the busy months. ‘Which is ironic,’ says Ralph. ‘Because we spent 300 years fighting the Scots. A lot of them ended up in our dungeon!’

With great fortune came great responsibility. Maintenance of the castle costs more than £1.5 million a year. Ralph and Jane had to make the castle work in the 21st century, as a home, a tourist spot and historical treasure, fighting against convention with a raft of visitor attractions, jousting sessions, gift shops and tearoom, and a few controversial decisions.

Ralph gave Jane an area of garden to revamp. ‘She was always mad about gardening, so I thought it was something for her to get her teeth into,’ he says.

Two decades, £45 million and equal measures of criticism and praise later, she has created an astonishing garden with a treetop walkway, treehouse restaurant and even a ‘poison garden’ (which specialises in toxic plants).

Amazingly, it is now the UK’s third most-visited garden — after Kew in London and Wisley in Surrey (though Ralph hasn’t set foot in it since last autumn).

In 2002, there was a big fuss when he sold a Raphael to America’s Getty Museum for £35 million. The National Gallery, which had restored the painting and had it on loan for ten years, was furious. ‘We needed to maximise the return; they felt we were being a bit greedy,’ explains Ralph. ‘But the painting was never here anyway.’

Meanwhile, he invited more and more film crews in. Over the years, the castle has featured as a backdrop for Blackadder, Robin Hood: Prince Of Thieves, Elizabeth, Mary Queen Of Scots, Transformers and the Christmas special of Downton Abbey. But it was Harry Potter — and, in particular, the broomstick lessons and Quidditch matches — that really changed things. ‘There’s been a huge Harry Potter effect and we’re very grateful for it,’ says Ralph. ‘We do as much Harry Potter stuff as possible and it just doesn’t seem to die out.’

Over the centuries, Alnwick has had so many incarnations, lurching from good fortune to bad and back again with every new monarch. During the Reformation and Counter-Reformation, the Percys abandoned Alnwick as the north was considered too dangerous. By the 18th century they were back, and the place was abuzz. There was a staff of more than 200 maids, cooks, valets, butlers, grooms, ten priests and, at one point, even a resident executioner.

The library at Alnwick castle, the Duke of Northumberland Ralph Percy's home

Today, the 150-strong staff seems to consist mostly of guides, shop assistants, cafe workers and gardeners. The Percys themselves have a daily as well as a chef.

‘People think we lead a very different life, but we really don’t,’ says Ralph.

Indeed, their living quarters are surprisingly cosy — taking in just eight of the castle’s 20 bedrooms.

But most people don’t have an enormous snooker table in their living room or an indoor tennis court. Or, for that matter, host a family wedding in 2013, where Prince William broke a tooth while dancing and had to be rushed off for emergency dental surgery.

And most of us don’t sleep in a tower, 140 steps up. ‘As we get older that gets more complicated,’ says Ralph. ‘And if you have dogs feeling ill in the night, it’s a long way to come back down again.’

There are dozens of other animals around the place: a rat running along a skirting board; a squirrel shooting up bookcases in the library; and more than 20 dogs — all stuffed.

‘They’re not our dogs!’ says Ralph. ‘Jane just buys random dogs that have been stuffed.’

It is now a quarter of a century since family tragedy changed everything but, while the 12th Duke knows he can never go back to his old life, he still occasionally yearns for a quieter existence.

‘I love this place. It’s fantastic, but it is living in an office to some extent,’ he says.

Which is why, after all their hard work, he has no intention of being carried out in a box.

‘George has control of Syon House and the Southern Estates, so whenever he feels ready, we’ll move out,’ he says. ‘I’ve always been rather jealous of Bamburgh Castle [just up the road from Alnwick]...’