Interview: David Walliams, actor and comedian

But watching the redoubtable Fiennes in action, Walliams recalls, “you suddenly go, ‘Hmm, maybe I’m not an actor…’”

But if he’s not an actor, Walliams is still willing to have a go. For another scene, he had to drive himself and the 13-year-old playing Pip in a horse and cart, something he’d never done before. He had two practices, went for a take, and “shot off” really fast. “And Mike Newell says, ‘I’ve worked you out, Walliams – you have no fear. That’s why you can swim the Thames.’ And I thought, ‘He’s actually quite right.’

“I don’t have a fear factor. Well, not much of one. And I’m willing to risk quite a lot – as a comedian, you’re always risking a lot. You’re risking failure, especially if you’re improvising and going on TV shows trying to make comedy out of thin air. That is quite a risky business.”

Later this month, Walliams will be seen doing just that. Alongside Simon Cowell and Alesha Dixon, he’s a judge on the upcoming series of Britain’s Got Talent. But just last week we saw him embrace an even tougher gig. There he was on telly, in the BBC documentary about his Sport Relief charity swim of the Thames. It was impressive stuff. Especially the bit where he was filmed scantily-clad, throwing shapes in his hotel room.

David Walliams Vs the Thames is a revealing portrait of his gruelling chug along the 140-mile length of the river. In eye-watering detail, it depicts the staggering challenges faced by the seemingly foppish funnyman, warts, rashes, torn spinal discs and all. Even before last week’s broadcast, Walliams’s indubitably courageous endeavour had raised over £1 million to help homeless children in Kenya. “I think its probably the most revealing thing of what I’m really like,” he says of a doc that didn’t stint on shots of a knackered and traumatised Walliams struggling to complete a challenge significantly greater than his 2006 swimming of the English Channel.

“Especially when you see me dance in my swimming trunks to ‘Dancing Queen’. That’s how I spend my afternoons,” he adds with a twitch of those camply expressive lips.

But Walliams – a super-successful entertainer with a Teflon chutzpah and a supermodel wife (he married Lara Stone in 2010 after a whirlwind romance) – relishes the chance to let it all hang out. Yes, as he cavorted in his budgie-smugglers in front of the cameras, he hardly seemed a prime physical specimen before he began the swim, last September, “I was already bulky. And I stayed bulky. But I did put on weight to do the Channel swim, about a stone and a half. I ate cupcakes. Why? Because they’re delicious and I’ve got a real sweet tooth. And also big chunks of cheddar cheese, and biscuits.”

Equally, he’s not afraid to admit – both on camera and in interview – that he was concerned he might fail his eight-day Sport Relief challenge. “Yeah, I thought I’d need at least a day out of the water. Then all of sudden it starts to become, ‘Oh, is it going to be ten days, 14 days?’ And it’s hard on all the other people in the team as well – a lot of people had given up their time for free and they needed to go back to their jobs. So I was concerned.

“And also, the longer it takes, the more boring the whole thing becomes. I don’t know if you can engage the public’s interest for that long. It’s like people who sail around the world – by the time they get back everyone has forgotten they ever left. I remember seeing on the news that Ellen MacArthur had come back. I was like, ‘Oh yeah, she went away…’”

But as he splashed his way through the Home Counties towards London, Walliams ploughed doggedly onwards, buoyed by the cheering riverside crowds who, each day, from dawn to dusk, turned out to give him encouragement. “It’s just a nice feeling,” he admits, “people appreciating what you’re doing. And getting involved and being interested in it as well. And I’ve noticed that once you leave London you do kind of become a bit more famous. People in London are a bit too cool for school. It’s not so unusual to see someone from London in the street. But outside of London people are a bit more excited to see you and come out and support you.”

Over the last few weeks, Walliams has been testing his fame factor the length and breadth of the country. The regional auditions for Britain’s Got Talent have taken him to most of the UK’s major cities. After our interview he’s travelling across to London to hop on Cowell’s private jet to fly to Edinburgh for the penultimate stop of the preliminary rounds. “It wasn’t something I thought I was ever gonna do,” he says of the reality TV ratings juggernaut that gave the world Susan Boyle. “But Simon asked me once before, then they asked me again. And I though, ‘Well, if he thinks I can do it, maybe I can do it…’”

Is it fun? “It is,” he nods. “It’s not like doing other TV shows. I’ve done panel shows, which I enjoy, and on those you’re recording half-an-hour of TV and sometimes they film for two hours. But with Britain’s Got Talent, you’re on camera for eight hours, with a large theatre audience watching – and in between you’re being filmed for ITV2 as you eat your lunch. So that part is quite hard to get your head around, because at any moment anything you say or do might get filmed.”

He admits that, even for a showbiz stalwart of his experience, working as a comic “without a script” is a little out of his comfort zone. It’s a challenge “just reacting to things and remembering to not say the wrong things”. He also feared using the buzzer. When he used to watch the show at home in north London – Walliams bought Noel Gallagher’s old pad, the Britpop-era party gaff dubbed Supernova Heights – he used to wince when the judges had to stop a performer mid-flow. But now he has realised, “actually, sometimes you’re saving them from humiliation. Because the audience are very vocal when they don’t like something. They start booing. There’s nothing worse than seeing someone onstage struggling.”

His biggest concern, though, was the presence of the all-powerful boss man. “But what I worried most about was, would Simon find me funny? I’m reasonably expecting to make the audience laugh. But before [we started], I asked the producers, ‘Can you make jokes about Simon? Can you make jokes about him being camp?’”

Walliams shakes his head in reply. “Can you make jokes about his friendship with Sinitta? No, no, no, no. Can you make jokes about his height. No way. Can you make jokes about his hair? No. His trousers? He has had so many jokes about them, he doesn’t like it. Oh, well,” mused Walliams, “what’s left?”

He didn’t have to wait long to find out. “The first contestant came out on the first day [of auditions], in Manchester, and I said, ‘What’s your dream?’ And they said, ‘To perform in front of the Queen.’ And I went [gestures along imaginary judging panel], ‘Well, here he is, go ahead…!’ And Simon was laughing, and the audience were laughing.

“It’s not the funniest joke, but they love to see Simon brought down a bit. Because he’s on this pedestal, isn’t he? It’s incredible. Then after that I thought, ‘Oh, it’s going to be fine… Simon’s going to be fine with a joke at his expense.’”

Walliams may have a healthy ego, but he’s also easy-going and eager to please. Does he have the requisite nasty bone to be harshly judgemental? “I think fair,” he counters. “And sometimes that judgement will be a negative judgement.”

The drive – for the spotlight, for public approval, for the good of others – that propelled Walliams to undertake his lung-bursting swimming marathons is keeping him busy elsewhere too. He’s writing a screenplay adaptation of his novel Mr Stink and a new children’s book.

He says he’s eternally gratified to meet parents who – myself included – thank him for persuading recalcitrant young boys to read. “When we were kids, computer games didn’t go on for ten hours. And there wasn’t even videos or DVD players. So a book felt like an option, didn’t it? Now a book is far down the list of the fun things you can be doing.’

He’s also writing an autobiography. With typical pithy knowingness, it’s to be titled Camp David. The book will cover his life, from middle-class childhood in Surrey to private-school education up to 2003, the year Little Britain took off. Having read other celebrity memoirs, he has realised that the “struggle” is the interesting stuff, not the years of success.

Then there’s the Agatha Christie series he’s “putting together” for him to star in with “a very famous female comedian”, but it’s not signed, sealed and delivered yet. “They’re Agatha Christie stories but [featuring] detectives people haven’t really seen before.”

And he’s not retiring his Speedos just yet. Walliams would like to have a crack at a travelogue series where he swim sround the world. Not literally – his inspiration is the 1968 Burt Lancaster film The Swimmer, “where he goes on a journey by water”, later immortalised in a Levi’s advert. “It won’t be quite as erotic as the Levi’s advert,” he adds with a smirk.

Oh, and there’s another film project about to kick off. He and Steve Coogan are starring in a biopic of Paul Raymond. “Of course,” he says with a smile, Coogan is playing the Soho property magnate and pornographer. “He’s going to enjoy that. I’m playing his priest – Paul Raymond shared a priest with the Queen.”

And what of Matt Lucas? Are he and his erstwhile Little Britain partner working on a follow-up to their misfiring airport-set sketch show Come Fly With Me? Not at the moment. Lucas is in America, “which he has always loved”, making films. He has just had a “major part” in the new movie from pop video maker and director Jonas Åkerlund. “I think at the moment he’s pursuing his Hollywood … let’s say career, because dream seems like it’s out of reach. Whereas I’m sure Matt has enough talent to have a good career there.”

Lucas has tried to persuade him to join him in Los Angeles, but Walliams has been resistant. Having “dabbled with it” when filming a small role in the Steve Carell comedy Dinner For Schmucks, he knows that “if you want to be a successful British person in America you do actually have to be there.”

He cites the case of Sacha Baron Cohen. “Ricky Gervais would have you believe otherwise,” he says with an arch of those expressive eyebrows, “but Sacha Baron Cohen is the most successful British comedian in the world. He has had a number of massive film successes there. He has properly got a career – he has worked with Tim Burton and Martin Scorsese and he has done his own films.”

But even for a man of Walliams’s ambition, at this stage in his career such a route doesn’t appeal. He doesn’t want to relocate to Los Angeles “for probably a slightly pathetic reason – I just think it would be like starting again. I’m not sure I personally would be that fulfilled playing supporting roles in Hollywood comedies. Dinner For Schmucks was fun, but I’m not sure that would fulfill me. If you can be the lead, like Sacha is, that would be fantastic. But,” he shrugs, “I’m not in that position.”

No, he’s not. But arguably – actually, inarguably – on account of those Herculean swimming triumphs, Walliams is in a better position. He’s now something of a folk hero in Britain. “Well, that’s nice. I’ll take that. I’ll run with that. For now…” he smiles.

“But it moves on quickly. Definitely people I meet always want to talk to me about it. So I think it has resonated with people. Whether it’ll be the same in years to come … I can’t worry about that. My day-job will remain trying to be funny.”