Jeremy Piven: From Entourage to period drama Mr Selfridge

He stole the show in Entourage. Now he is taking over Sunday nights as the star of Andrew Davies' new drama. James Rampton meets him

The American actor Jeremy Piven is best known as Ari Gold, the manic, manipulative, magnetic Hollywood agent who stole almost every scene he was in over eight series of Entourage. Gold is the sort of character likely to be found closing deals while schmoozing the glitterati in the South of France. So it is quite a turn-up to meet Piven in the decidedly unglamorous surroundings of a former carpet warehouse in Neasden, north-west London. "For my next project, I was thinking, 'it's either going to be Nice or Neasden'", he deadpans as we shake hands. "Then I decided, 'let's go for Neasden...'"

The actor is in Neasden to play the title role in Mr Selfridge, ITV1's major New Year period drama about the birth of the British department store. Face-to-face, Piven, 47, looking resplendent in his character's full beard, a jaunty cap perched on his head and a blue bandana around his neck, is just as you would hope: a fizzing ball of energy, with more charisma in his left toenail than most of us possess in our entire bodies. He may not tell me to "hug it out, bitch" as his famous alter-ego was keen on saying, but he is gifted with a deft, self-deprecating sense of humour. And he's thrilled to be working in the UK.

"I have been such a fan of British television ever since Monty Python. There is so much quality control. You do 10 episodes, work really hard on them and get them absolutely right. In the US, we do 116,000 episodes of everything. I remember once meeting Al Pacino. He had seen some episodes of Entourage, and he just said to me [at this point Piven breaks into a flawless Pacino impersonation], 'WHEN does it end?'"

Piven, with enough spark to light a blast furnace, is ideal casting as the mesmerising Harry Selfridge. Variously nicknamed "the Earl of Oxford Street," for his vast wealth, and "Mile a minute Harry" thanks to his insatiable energy, the American was a veritable force of nature. And he lived a life that was made for drama. Set in 1909, Andrew Davies' 10-part adaptation of Lindy Woodhead's biography, Shopping, Seduction and Mr Selfridge, depicts the rise and fall of the man who invented the modern-day department store. By opening his eponymous shop on Oxford Street at a time when women were enjoying a new sense of liberation and could walk out unchaperoned for the first time, Selfridge changed the face of retail. His aim was to make shopping as exciting as sex. He came up with the phrase, "the customer is always right", and broke new ground by pioneering window displays, wedding lists and celebrity endorsement. A sometimes reckless pioneer, Selfridge wanted his store to be a theatre of retail.

ITV1 has invested a lot of time, money and effort in this grand new 10-part series. It is 76-year-old Davies's first period drama since South Riding two years ago, weighs in at a reported £1m per episode and has already been dubbed "Downton Abbey with tills". Doubtless the broadcaster is hoping that Mr Selfridge will emulate the immense global success of Julian Fellowes's period drama and rival the immense popularity of its Sunday-night competition on BBC1, Call the Midwife.

Inside the gigantic former carpet warehouse, the set designers have done a splendid job of recreating the 1909 shop floor. As you wander around the cavernous, yet beautifully dressed, set, you are overwhelmed by period detail – a sheath of silver-top canes here, a rack of women's feathery hats there. The ostentatious displays mirror that era before the First World War when Britannia still ruled the waves with an untrammelled sense of Imperial entitlement. You could easily imagine the "upstairs" characters from Downton Abbey coming to shop here.

In the opening sequence of the drama, which begins tomorrow night, the visionary entrepreneur is touring the shop floor, rallying his retail troops before the shop's grand opening: "I want Treasure Island in here, Aladdin's Caves… We're making history here… We're going to dazzle the world… London is crying out for this. We're giving them style, glamour, razzamatazz. Once they see what we've done here, there will be no turning back!"

It is the perfect match of performer and part, and it's no surprise to hear that Piven was instantly drawn to this natural showman. "I'm playing up the theatrical side of Harry's character. I'm fully invested in that idea. He was a huge fan of PT Barnum, and so much of his concept of how to run a department store was based on promotion and showmanship.

"For instance, he brought in Henri Leclair from Paris, who was a genius with window displays. That was revolutionary. His windows were works of art. Selfridge would stage 'living moments' that drew people from all over. We just shot a scene in which he convinced Blériot to put his plane in the store. Unbelievable!" In 1925, Selfridges hosted the first ever public demonstration of a working television by John Logie Baird.

Selfridge was also driven by an insuperable sense of self-belief. The actor, who hails from Chicago, where his alter ego worked, says: "The money for the store fell through at the last minute – and yet he was still so sure of himself that he willed it to happen. There was a real culture clash. Harry had this American, can-do attitude which contrasted with the British who were very realistic or, some might say, pessimistic or nihilistic – in fact any '-istic' you care to mention! He was a spirited American guy who just made things happen through the sheer force of his will."

Selfridge was also ahead of his time in his unashamed use of self-publicity. "Harry was a celebrity, and he loved the attention. He was the first celebrity who was available to the general public every day. He liked taking a victory lap, but people over here thought that was uncouth. People in this country are a little more civilised and humble. They think, 'you have to work hard and let that speak for itself'. I'm playing him as a ray of sunshine," says Piven. "He's doing emotional kung fu on people to convince them. They're saying, 'we're doomed – it will never happen', and he tells them, 'it's going to be OK'. He's a ray of sunshine on a rainy London day."

But Mr Selfridge is no mere snow job; the title character is portrayed as deeply flawed. Piven observes: "Harry had a huge heart. But he was a slave to his vices, and Andrew's script really taps into those demons. For a start, he was a massive gambler. He felt most alive when the stakes were highest. While it scared the hell out of the people around him, it was thrilling to him. But it would eventually lead to his downfall." He died a pauper in 1947, unable even to afford a headstone.

A man who thrived on taking risks in all aspects of his life, Selfridge was also an inveterate womaniser. In real life, the married father of four had dalliances with the dancers Isadora Duncan and Anna Pavlova, and the French singer Gaby Deslys. After the death of his beloved wife, Rosalie (played by Frances O'Connor), Selfridge went seriously off the rails, lavishing money on a succession of mistresses. A pair of dancing twins, the felicitously named Jenny and Rosie Dolly, were said to have frittered away in excess of £5m of his money.

Davies, the writer famous for "sexing up" such classics as Pride and Prejudice and Northanger Abbey, has not stinted on the raunch factor in Mr Selfridge. Known as "the man who put the 'cor!' into corset dramas", Davies says that he has written in as much nudity, "as you can get within the limits of prime-time viewing". In the drama, Selfridge enjoys an affair with the noted actress, Ellen Love (Zoe Tapper), among others. Piven can see where his philandering character is coming from: "Even though Harry was very much in love with his wife, he still fell for other women. You might not agree with what he did, but you can see that the temptation was so strong. When his wife and mother died, he was destroyed. That's when the wheels really fell off the wagon. All in all, it was quite a journey."

As for Piven's journey, he was always destined to be an actor. His parents, Joyce and Byrne, started the acclaimed Piven Theatre Workshop in Chicago, which also launched the careers of Aidan Quinn, Joan Cusack and John Cusack (a friend of Piven's since high school). This theatre background made Piven feel instantly at ease in Britain.

"I love it here," he says. "You can be whoever you are. I studied Shakespeare at the National Theatre back in the day, so I have a reference for this place. I grew up on stage, and I feel I have had a very similar journey to a lot of the actors here. They take it very seriously. I can warm my voice up between takes, and no one bats an eyelid. I feel very much at home here."

After graduating from Drake University in Des Moines, Iowa, Piven landed his first major TV role in 1992 playing the lead writer in HBO's long-running comedy, The Larry Sanders Show. He went on to appear in movies such as Runaway Jury, Old School, Black Hawk Down, Serendipity and Rocknrolla.

His breakthrough came in 1994, when he was cast as Ari Gold, the foul-mouthed yet mesmerising agent to Hollywood glamour boy Vince Chase (Adrian Grenier) who became famed for Gold-isms like, "we are gonna get drunk with Russell Crowe and we're gonna head-butt some goddamn kangaroos". Or, when trying to put Chase off a poorly-paying movie, charming advice like, "You know what they feed people on an indie set, Vince? Nothing! They don't give you a trailer. They tell you to go sit on an apple box. Ever try to bang an extra on an apple box?"?

Inspiration wasn't hard to come by. Hollywood, says Piven, is full of amoral chancers like Ari. "We could walk around this block, and gather up eight or nine agents and write four more seasons. If I can't find inspiration for this guy, I need to go back to Chicago and start cleaning tanning beds."

For now, Piven lives alone in Malibu where Ari fans often come up to him and put him in a headlock as a sign of affection. "People think that behaviour is normal around Ari. It's a weird compliment, I guess."

It was the role of a lifetime and earned Piven three Emmys and a Golden Globe. "Entourage struck such a chord because, like Mr Selfridge, it was based on a true story," he says. "We tried to be authentic as possible about the backstage life of Hollywood. Those characters existed, and we were trying to depict them as accurately as we could. Viewers are also fascinated by people who have to rise to the occasion. In Entourage, you had an actor trying to navigate becoming a star and the world that suddenly surrounded him. Audiences responded to that."

They also warmed to Gold's alpha-male unpredictability. The character could, "snap your head off, reach into you, pull out your integrity, cackle and then tell you how much he loves you in the next sentence".

Back in Neasden, has Piven found time in his shooting schedule to visit the real Selfridges? "Yes. It's amazing. They take it very seriously. What Harry set up still lives on in a very strong way. His presence is still there. The staff are very knowledgeable. I managed to go into the store and buy a jacket under the radar," he grins. "I don't know if that will last forever, given that I'm now playing Mr Selfridge."

Next time, I imagine, he may well get a personal shopper.

'Mr Selfridge' begins tomorrow at 9pm on ITV1

The man who put the 'cor' in corsets: Five of Andrew Davies's best period dramas

Middlemarch (1994) Davies announced himself as a major-league adaptor of period blockbusters with this gripping interpretation of George Eliot's novel.

Pride and Prejudice (1995) This Jane Austen adaptation stirred countless female hearts – including Bridget Jones's – by inventing a scene in which Mr Darcy (Colin Firth) emerged from a lake with a white shirt clinging to his wet chest.

Tipping the Velvet (2002) The writer attracted huge audiences – and many headlines – with his characteristically steamy reworking of the Sarah Waters novel about Victorian lesbians, starring Keeley Hawes and Rachael Stirling.

Bleak House (2005) Davies changed the face of TV costume drama with this groundbreaking version of the classic Charles Dickens novel, which was broadcast like a soap in half-hour episodes.

Little Dorrit (2008) Davies hit the ratings jackpot and proved himself an acute interpreter of Dickens with this memorable reading.