His day job might be all courtrooms, drama and deadlines, but catch Scott Turow at one of his gigs and you'll find him thrashing around on stage in a wig - while Stephen King plays guitar. The bestselling author tells Hannah Stephenson about his double life, old pal Obama and the real-life inspiration behind his latest book.

Like his gripping legal thrillers, bestselling author Scott Turow is full of surprises.

Welcoming me into his hotel suite, this short, balding man with a laconic tone - whose debut novel Presumed Innocent was made into a hit film starring Harrison Ford and Greta Scacchi - seems every inch the academic who always wanted to be a writer.

Yet, as well as being a practising lawyer in his hometown, Chicago, where he first met his old pal Barack Obama, and a bestselling author whose books have sold more than 30 million copies worldwide, Turow also has a wilder side - though, meeting him for the first time, you wouldn't know it.

He's the singer in a band of writers called The Rock Bottom Remainders, the most famous of whom is horror master Stephen King.

The band was founded by the late Kathi Goldmark. Other authors who join in include Dave Barry, Mitch Albom, Amy Tan, Greg Iles, Ridley Pearson, James McBride and Roy Blount.

"We do Sixties covers. I sing - badly. Sometimes to amuse themselves, they'll describe me as the lead vocalist, but it's just an act of false humility on the part of the rest of them," Turow observes.

For the gigs - they've played some major venues in the US - Turow will discard his conservative daywear and don zany wigs (he has a huge collection).

"I'm up there to make a fool of myself. I wear jeans, a feather boa and a wig. We'll play to anybody who doesn't care about hearing good music. The audience is there out of literary interest, rather than musical."

Stephen King plays rhythm guitar and is a fabulous performer, Turow muses.

"Compared to me, Stephen King is Mozart," he says, erupting into laughter.

"I remember one time I jumped back from the audio monitor because there was some awful sound coming out of it. I said to Kathi, 'What is that?', and she said, 'It's Steve, he's singing'.

"My main contribution to this band is as a sight gag, it's certainly not my musical ability."

Turow's in the UK promoting his latest thriller, Identical, which sees a man pleading guilty to the murder of his girlfriend, the daughter of an influential businessman and politician.

He's released 25 years later into the care of his identical twin, a mayoral candidate in the middle of a political campaign, who's then subjected to damning allegations that he was somehow also involved in the crime.

Turow, 64, was inspired by his own family experience as a child.

"When I was three, my sister was born and was supposed to be a twin. I had been fully prepped that when Mum came back from hospital, she'd bring back two babies.

"But only my sister came. It was announced that the other child had died in childbirth, strangled by the umbilical cord. This was very confusing for me, particularly as my father was an OB [obstetrician], so he delivered babies, and everybody else's babies seemed to come out healthy and happy.

"It turned out that the other baby was a boy. I wondered if the reason the other baby didn't come home was because he was a boy like me," he adds.

"I became engaged with the fantasy that this other baby had actually been my twin. I strongly recall pining for this lost brother and being caught up in the idea of having an identical twin."

Turow says he had a difficult relationship with his father, David, an eminent physician.

"He needed my mother to himself, and the arrival of children presented him with rivals for her attention, which he didn't necessarily welcome. He was always angry with my sister and me."

Writing was Turow's first ambition. After graduating, he taught creative writing at Stanford University and was set for a career as an academic, when the law came to his attention.

"It was a total surprise. When my room-mates came out of Harvard Law School and started practising, I thought that was really exciting."

He enrolled at Harvard and a legal career followed, both as a prosecutor and a defender. Today, he divides his time between writing and working on white-collar criminal defence cases and devotes much of his time to pro bono matters.

His insight into politics and the legal profession, so prevalent in many of his books, is taken from personal experience.

Indeed, he supported Obama (they met as lawyers) during his early days in politics, but they've seen little of each other since Obama became President.

"We really met through writing. He had just published Dreams From My Father and I sent him a note saying how much I liked it. We became social friends and on occasions we had dinner together.

"I often refer to the president as a guy I used to know, because he has more pressing things to do than stay in touch with all his old friends in Chicago," he reflects.

He saw Obama in March 2012 at a fundraiser and receives Christmas cards from him, but that's about all, he says.

"If he's back in Chicago, I assume our paths will cross."

Although four of his novels have been adapted for film or TV, he's never quite enjoyed the screen success that he had with Presumed Innocent, back in 1990.

"With the exception of Ordinary Heroes, every book I've written has been optioned. There have been a number of films, two TV mini-series, one TV movie, a pilot for a weekly series. I'm not lacking in experience in that world. I've cashed many cheques."

Identical has not, however, been sold yet.

"Right now, the world of features isn't looking to courtroom stuff. You'd have a hard time naming a courtroom movie that's been made in the last five years. Their view is that the courtroom belongs to television now.

"The best source of material has been comic books in the last several years."

While his writing and law careers have continued to flourish, his personal life has had its ups and downs.

Seven years ago, he divorced his wife of 35 years, painter Annette Weisberg.

"That was the hardest thing I'll ever do, but for me it was the right decision," he reflects. "The more distance I get on my marriage, the more I recognise that when a long marriage starts to go wrong, it's like any system that starts to fail. Mistakes keep repeating themselves and the further away I get, the less blame I cast or feel.

"The marriage went off the tracks. It's taken a while, but we now have a very respectful relationship that recognises we spent the bulk of our adult lives together."

They have three grown-up children and Turow now lives with his girlfriend, a lawyer he hired at his firm more than 25 years ago.

"We were professional colleagues, then she became a neighbour years later, but at no point was there any thought of romance. It's come as an enormous surprise for both of us."

He's now working on a young adult novel, before moving on to another courtroom thriller, but for now his ambition is to be a good grandfather to his grandson, born last year.

"Being a grandfather is pure joy," says Turow. "It's so revitalising to have a baby in your life again."

:: Identical by Scott Turow is published by Mantle, priced £18.99. Available now