'It's a bit like the X-Files if it was set in 1901'
Stephen Mangan grapples with some very big questions in his new supernatural crime series, Houdini & Doyle. He discusses life after death with Ella Walker and insists he is really The Stig on the new Top Gear.
Stephen Mangan is being uncharacteristically serious. "It's a question we all have to wrestle with at some point: do you carry on after you die? Are the dead still with us in some way? Can they communicate with us? Is there such a thing as the paranormal? Are there psychics?"
It seems a sober opener for a stage and screen actor whose breakout role was as Adrian Mole in The Cappuccino Years on BBC One, and who's best known for appearing in comedies like Episodes and Green Wing, as well as for playing a pregnant man on stage at the Royal Court.
But the curly-haired father-of-two is playing Sherlock author Arthur Conan Doyle, opposite Michael Weston as American illusionist and stunt artist Harry Houdini, in a new crime caper.
Houdini & Doyle sees the duo investigate murdered nuns and encounter aliens, but at its core, it's an exploration of spirituality, and what, if anything, comes after death.
"Doyle is a rationalist, but he believes in the supernatural and the spiritual world, and he wants to prove it scientifically," explains London-born Mangan. "It's a sort of Edwardian X-Files, where one believes and one doesn't and they're trying to battle it out."
"I'm pretty on the Houdini side," he admits, noting he is, after all, a former altar boy turned atheist. "But having said that, what filming this has made me realise is that we all explain the world around us through stories.
"I think all human beings, for some instinctive reason, understand the world through stories, even my kids [he has two boys], their history, it becomes a series of stories. Things that they do, or that we did as a family, become a story that often is quite far from what actually happened, but it doesn't matter, because the story becomes more important.
"I've realised that, whether something is technically true, even if you can define what that is, it's sort of unimportant. It's sort of unimportant whether there is or isn't a God. If someone believes there is and bases their life around that, then for that person, God exists.
"You have to look at young men and women blowing themselves up in the name of religious stories. How powerful is that?
"Whether I believe in the afterlife or the spirit world, or I don't, the story I tell myself is important. Whether the afterlife actually exists or not, who cares?"
Although Houdini and Doyle were real-life acquaintances, the team behind the new show have "mucked about" with the period, with when they knew each other and with what they were up to at the time. "If people are expecting a documentary about 1901, they might be disappointed," Mangan jokes.
However, when it comes to the show's attention to detail and what it was like stepping out on set, he says, "it was like being in a time machine" - and the levels of authenticity even stretch to his facial hair.
"The moustache is my own moustache," he says, somewhat proudly. "I was given a picture of Tom Selleck in Magnum and told to 'grow that'. It took me six weeks - in the first episode or two you can see it's still being cultivated. It gets more bushy as the series goes on. My wife nearly divorced me. She hated it!"
When it comes to crime drama in general, Mangan is unequivocal: "The purest crime drama there is - and the best - is Scooby Doo". And he should know: the 47-year-old doesn't watch much else at home. Not even Sherlock. In fact, before taking on the role of Doyle, he hadn't read anything by the writer.
"I hadn't read any of his books, I'm embarrassed to say. It was the same when I played Bertie Wooster a few years ago [in the Olivier Award-winning comedy Perfect Nonsense], I hadn't read any Wodehouse," he admits.
"The list of iconic TV that I've yet to see is long and embarrassing: The West Wing, The Sopranos, Breaking Bad, The Wire - I've not seen any of them."
He's easily forgiven; after all, this is the man who played the hilariously obnoxious anaesthetist Guy Secretan in cult comedy Green Wing on Channel 4, alongside Julian Rhind-Tutt and his Episodes co-star Tamsin Greig.
The show ended in 2007 after two series and Mangan doesn't hold out much hope for it being brought back for a third. "I would be surprised. I just can't imagine you'd get all those people together again."
What about a Secretan spin-off?
"My only worry about playing Guy again would be that he's already a hero to anaesthetists, and if any group of people have Guy Secretan as their hero, then they need to take a long hard look at themselves!" he says with a laugh. "My advice would be: don't get ill, don't have an operation!"
In April, Mangan will be filming the final series of Golden Globe-nominated sitcom Episodes, and has every faith that his long-time co-star Matt LeBlanc will, as host on the new version of Top Gear, make the car show his own.
"I think he'll do really well. He's a total car nut. He's genuinely knowledgeable about cars and interested. He did that fastest-ever lap by a celebrity on Top Gear, so not only can he drive, but if you watch him do that lap, he gives a running comedy routine on the way round which is really funny, so it's pretty impressive."
Witty as ever, Mangan would like to have us believe that he'll still be working with LeBlanc, post-Episodes though.
"I am The Stig!" he says wryly. "That was his stipulation, if he does Top Gear, Mangan has to be The Stig!"
Here's hoping ...
Houdini & Doyle, ITV, tomorrow, 10.15pm