"If it had been a hazy, nostalgic 1970s trip with Noddy Holder running around and funny accents going on, I wouldn't have done it," says John Simm. "There were some very dark things going on in the 1970s - racism, strikes, the Birmingham Six, the Guildford Four - and we need to reflect that in Life on Mars."
One of the best actors of his generation, and long a cult star and unlikely sex symbol, Simm, 36, has been threatening to hit the big time for a while. State of Play raised his profile. But it was the time-travelling cop show Life on Mars that put him on the map. Not only did the show pull in more than seven million viewers, the DVD became one of last year's biggest sellers. In November, Life on Mars won Best Drama Series at the International Emmy Awards. And Hollywood producer David E Kelley (of Ally McBeal fame) is planning to make a US version.
Simm's career has gone through the roof. But you sense he's slightly horrified that Life on Mars has made him so bankable. "I've never done anything so mainstream and glossy before," he admits.
He is endearingly bad at being famous. He rarely goes to premieres and he and his actress wife, Kate MacGowan, nearly didn't get married because they loathed the idea of being splashed across Hello!. "I don't do things for money," he says, half sighing at his own foolishness.
But then Simm has real street cred. Before becoming a professional actor he started his band, Magic Alex (named after The Beatles' electrician), and toured with Echo and the Bunnymen in the early 1990s. After he played New Order frontman Bernard Sumner in Michael Winterbottom's 2002 film 24 Hour Party People, he was invited to sing on stage with the band.
Because of his roles, audiences often assume Simm is a bit of a lad. But he trained as a classical actor and his interests are eclectic. He has started going to ballet ("I'm obsessed with it"), and his favourite painters are Van Gogh and Jackson Pollock. "I remember on a stag weekend in Amsterdam queuing for a whole day to try and get into the Van Gogh museum," he recalls.
Family life is very important. He and MacGowan live in Crouch End in London with their five-year-old son, Ryan, and he admits filming Life on Mars in Manchester for two summers was tricky. "It was hard coming back to London for Sunday lunch, trying to cram everything into one day off. I can't possibly do that again."
Born in Leeds in 1970, he grew up in the mill town of Nelson, near Burnley. After his parents split up, when he was 11, he'd accompany his father, an entertainer, touring the northern clubs. Simm became a talented guitarist, but never enjoyed the spotlight. Acting is easier, he says; you can pretend to be someone else. "But in a band, on stage... there's nowhere to hide. I used to just stand there and stare at the floor."
After drama school his breakthrough role came in 1995 as a psychotic teenager in Cracker. In his twenties he played sweet-faced, hedonistic young men (Danny in The Lakes, Jip the clubber in Human Traffic) and became an alternative sex symbol. More recently he's excelled in gritty roles such as Michael Winterbottom's Wonderland and Abi Morgan's Bafta-winning drama Sex Traffic, about Eastern European girls kidnapped and forced into prostitution in the West. "I don't mean to sound wanky, but I think Sex Traffic was a really important piece of TV... They even made a documentary called The Real Sex Traffic. Suddenly it was an issue, and that's wonderful."
Simm has a slightly prickly reputation with journalists. He hates talking about his personal life (he once dated Emma Bunton, and the papers have never let him forget it). But in person he is funny and modest. In contrast to his naff 1970s wardrobe in Life on Mars, Simm is a snappy dresser (with a weakness for Paul Smith and Versace). He laughs when I suggest Life on Mars is an unacknowledged gay love story between his character, Sam, and his boss, Gene, played to great acclaim by Philip Glenister. "In a way, friendships at work are a kind of love story," he says.
But then Simm is refreshingly unmacho. During our interview some drunks start baying outside the window. "Knobheads with football scarves on," he sighs. "Sorry.I hate feeling snobby, but you think, you morons."
Simm has had his moments, too. He went a bit "ballistic" clubbing and taking ecstasy in the 1990s (he had to give up clubbing when Human Traffic fans started making his life a misery), but he says he is alienated by youth culture today. "I don't recognise kids any more: they've started going crazy and knifing and shooting each other." In the old days, he says, you got a clip round the ear. "My five-year-old's already going bang-bang-bang with his Power Ranger and chopping people's heads off. When I was five it was the Clangers and Sooty. There's no innocence any more. I feel really sorry for them."
These days, just having Simm's name above the titles is a guarantee of quality. When the producers first pitched Life on Mars, they suggested Neil Morrissey and Ray Winstone as the leads. No one got too excited. But when Simm's name came into the frame, it was snapped up.
The series returns on Tuesday. Audiences love the rollicking un-PC humour and 1970s jokes, but there is ambiguity, too. Has Sam really gone back to the 1970s, or is he in a coma - or dead?
Simm believes the series appeals to a key fantasy. "Everyone dreams about going back in time and meeting their parents when they were young. It's that thing of 'could you change the future?'"
Although he promised himself a long break after Life on Mars, he was immediately offered the chance to play Van Gogh in the Channel 4 film The Yellow House, opposite John Lynch as Gauguin. "There was no way on earth I could turn it down. The day before they told me, I had a beard, but I shaved it off to have a facial and go on holiday. When I heard I'd got the job, I was frantically looking in the mirror and going, "grow, grow". He also went on a crash diet to get his favourite artist's emaciated look.
Although the BBC is planning a spin-off to Life on Mars - called Ashes to Ashes, set in the 1980s and starring Glenister, Simm is bowing out. "My instinct tells me not to hang around too long."
He'd like to do some comedy "in warm weather - preferably on a beach. I always seem to be doing drama in horrible brick locations." And for years he's been dying to play a proper villain or a serial killer. The problem is Simm still looks 35 going on 15, but finally he's got the chance: he's just been cast in Dr Who - as the Master, the Doctor's evil nemesis. He'll be quite brilliant, of course, but heaven knows how he'll cope with a whole new horde of obsessive Tardis fans.
'Life on Mars' resumes on BBC1 on Tuesday at 9pm. 'The Yellow House' is on Channel 4 in April
Biography: The route from Leeds to Mars
Married to actress Kate MacGowan. The couple have a son, Ryan, aged five.
1970: Born in Leeds, grew up in Nelson, Lancashire. Attends Blackpool Drama College, then the Drama Centre in London.
1992: Makes his TV debut with a role in Rumpole of the Bailey.
1995: WinsBest Actor at Valencia Film Festival for Boston Kickout. Appears in Cracker.
1997: Stars in Jimmy McGovern's The Lakes.
1999: Film roles in Human Traffic and Wonderland.
2000: Features in Clocking Off.
2002: Plays New Order frontman Bernard Sumner in 24 Hour Party People and Raskolnikov in the BBC's Crime and Punishment. Sings on stage with New Order.
2003: Stars in State of Play with Bill Nighy and David Morrissey.
2004: Takes the lead in Channel 4 drama Sex Traffic.
2006: Plays Detective Inspector Sam Tyler in Life on Mars.
Likes: The Beatles, Ian Brown, Manchester United, Van Gogh, good manners, family life.
Dislikes: Heat magazine, tabloids, bigots, Arsenal, being away from his family.