Marcus Brigstocke: The comedian now arriving at Waterloo ...

... is turning his hand (and facial hair) to acting, having mastered stand-up, writing a book, and being an eco-hero and self-confessed hypocrite. Susie Mesure meets Marcus Brigstocke

(JASON ALDEN)

They itch, they offend his wife, and they are playing havoc with his book tour – but Marcus Brigstocke reckons the "chops" have one big selling point: "You know what, with that on [dons peaked cap] and the specs off [removes his trademark horn-rims], I look in the mirror and go, 'Good, good. I don't have to act too hard now.'"

He's joking, of course, as you'd expect of a comic, albeit one preparing to spend the next three months playing his biggest straight acting role to date. The sideburns – less Elvis Presley, more General Ambrose Burnside – are in honour of E Nesbit's Station Master Perks from The Railway Children, which returns to Waterloo station in London tonight. It may be his biggest part, but he's braced for the train to upstage him. Truth be told, we're sitting in the Old Gentleman's saloon carriage, which starred in the 1970 feature film, and I'm finding it hard to concentrate on Brigstocke's amusing stream of anecdotes.

He has mixed feelings about the chops. "It's a nightmare because I'm promoting my book, so everywhere I go people are like, 'Um, so just how much attention do you need?' And I'm like, 'Nononononononono, it's for a role'." He adds: "I came in for a photo shoot for the launch. I had a beard, and they held up a picture and went, 'We thought this.' And I went, [falsetto voice], 'Did you, did you?' And then they literally just went, 'Zooop', and took all that off." But he's happy with anything that takes "off the pressure", like going into something he already knows works well - the production won a coveted Olivier in March. "That said, you don't want to be the idiot who turns up and breaks it." Cue posh newsreader's voice: "The award winning production of The Railway Children was ruined today by a comedian with lofty ambitions."

He is loving the part, which to many will forever belong to Bernard Cribbins, the Perks in Lionel Jeffries's movie. "I heard something, I hope that it's true: Perks is the first working-class character in British literature to be drawn in a positive light. She's drawn him beautifully. He's just a lovely, lovely man, with a great big problem: his Yorkshire pride gets in the way."

What he particularly adores, though, is the venture itself: the action all takes place in Waterloo's old Eurostar terminal, a white elephant in the making when Eurostar switched to its new St Pancras home. "This is one of those things where people go, 'Well, that's a bloody waste of money,' but all of the different people – Railtrack, and the people who own the station, and the people who own the platform, and the people who own the turnstiles, and the square of carpet – all went, 'Oh, yes, oh, we can do that.' I mean, you read, 'Village fete cancelled because tree pollen poisoned child,' and no one's allowed to do anything any more, and then this massive thing with a real steam train arriving and nearly running over one of the cast happens, and I think that's really breathtaking."

If you think it funny (peculiar, not ha ha) that a 38-year-old comic is treading the boards in such a prominent part, bear in mind comedy was only ever something Brigstocke did on the side. Despite being the funny kid at school – mainly "because I was very willing to be naughty" – it took a massive prod from his best mate to get him in front of the stand-up mike. "He booked my first ever gig, and told me I had four days to write it. I had seven minutes on stage and died on my arse for the first four, but for the last three it just rocked. It was literally a total thunderbolt moment."

The seminal gig was at a Kiss FM talent show in 1995; he hasn't looked back, chucking in his drama degree at Bristol because "by the time I reached the end of my second year I was a full-time comic working every night, doing 1,000 miles a week".

The friend was James Ross. Was, because he died five years ago. He's also the reason that Brigstocke, an avowed atheist, has just written his first book, God Collar, which is out this week (subheading: "Are you there God? It's me, Marcus"). The autobiographical book follows a show that he wrote to explore the "God-shaped hole" that his friend's death left in his psyche.

It's a fun and interesting tramp through some of life's biggest questions. But if you're looking for answers, buy something else. "This is a book about confusion. In the same way that Dawkins tries to unify secularists, and the churches variously try to unify and bring people together, this is an attempt to unify the confused. Because there's an awful lot of us."

Despite exploring all of the big 'isms, plus the Church of England, he winds up as he started: an atheist. "I wouldn't be if I could be anything else, because I don't think it's any good. At least I don't think it's bad, but it's a blank page on which you have to impose a better philosophy, and I don't have one."

He argues the toss with tongue firmly in cheek, although he says the book, which takes in his troubled past – he was expelled from three schools and went to rehab aged 17, weighing 24 stone, for food, drink and drug addictions – is probably less sarcastic than his typical routines. "You read it back and go, 'How the hell are they supposed to know I'm being sarcastic.' I can't put two-thirds of the book in italics. And anyway I'd need three different forms of italics to point out when I'm deliberately overstating the point." Other pitfalls of the writer's life include the solitude. "No one claps when you finish a chapter. It's rubbish. How are you supposed to know if you're any good?"

Personally, I buy his conjecture, although perhaps I just like his gags. ("Religion and warfare are like Ant and Dec: you could have one without the other, but I couldn't see the point. If you want to wear a ring that tells everyone you're not having any sex then you can get married like the rest of us.") But doubtless Brigstocke's detractors will level the same charges of hypocrisy to his cod theorising as they do to the man himself. After all, the case for the prosecution is strong: he's a resoundingly middle-class, public-school-educated comedian, who made his name either railing against or riffing on the same bourgeois conventions that define his life. He's also a self-confessed eco-warrior (he spent £100,000 on a green makeover for his family's house in Wandsworth, in London's so-called Nappy Valley) who snowboards.

I ask how he squares the hypocrisy, but can't give him a hard time because his defence makes me smile. "You can't. You just can't. You just feel awful about it and add it to the list of things to wring your hands over."

He pauses, ostensibly to take another bite of his Marks & Sparks sarnie because I've caught him on a lunch break between rehearsals, and adds: "I'm a hypocrite. I lead a really hypocritical lifestyle. But I don't know anybody who doesn't really. Oh, that's not true. George Monbiot doesn't. But I don't want to be George Monbiot. I mean, I hope he's happy and everything. He's a nice fellow but I don't want to be him. And it's too hard, anyway." (Note, it's a pre-packaged M&S sandwich that presumably shortened the earth's life in the making.)

If you're wondering (and I was), the hypocrisy extends to sending his two children, Alfie, eight, and Emily, six, to private school. He whispers: "But don't tell anyone." Whoops. "It's an interesting one, that, because I have ethical problems with it, but it comes down to – and I'm not saying this is an excuse for poor ethical decisions – but it comes down to a really basic instinct, that Darwin described, of 'I will make the best environment for my children'. And I think this is the best environment for them."

The school is ostensibly secular, but he says there's more God than he had expected. Hence, Emily is already a believer. Witness a recent father-and-daughter moment in the park. "I was pushing Emily on the swing and she reached the top and shouted, 'I could kick Jesus from here.'" The Wandsworth mummies were unimpressed; Brigstocke "was in creases". For the record, Emily is also into "the Musselems" and the way they pray, head first. And Diwali. He adds: "She's keen on all that. And I'm not saying this in a glib way to be disrespectful, but she also loves fairies."

Hypocritical or not, Brigstocke's a hard man not to like. Unless, of course, I was just smitten by the glamour of that first-class Pullman carriage, all polished wood, carpets and silverware, and the romance of a 141-year-old steam locomotive.

Marcus Brigstocke plays Station Master Perks in York Theatre Royal's production of The Railway Children at Waterloo station

Curriculum vitae

1973 Born 8 May in Guildford, Surrey. His parents already had a daughter and another son followed much later. Father, a stockbroker in the City; mother, head of a local private school.

1980 Sent to boarding school after being expelled for the first time. But that doesn't stop him getting kicked out again four years later, and yet again aged 17.

1990 Years of battling eating, alcohol, and drug addictions see him enter rehab at a residential treatment centre. Recovers, and realises he wants to act.

1995 After stints at two drama schools in London, he goes to Bristol's Old Vic Theatre School. Finds comic fame mid-degree in a Kiss FM talent show, so drops out after two years.

1996 Wins the BBC's New Comedy Award.

2001 Appears in BBC family sitcom The Savages (pictured) Marries Sophie Prideaux. They have two children, Alfie, and Emily.

2003 Plays a DJ in Richard Curtis's Love Actually.

2005 Hosts The Late Edition, a topical news show.

2007 Goes on tour with his Planet Corduroy show.

2008 Starts the Altitude Comedy festival in Meribel, France.

2009 His show God Collar, exploring the "God-shaped hole" in his life, is a critical hit, and is now a book.

2010 Plays King Arthur in Spamalot.

2011 Plays Mr Perks in The Railway Children.