David Walliams says he can be serious too, as he stars in BBC1's Partners In Crime

The 43-year-old comedian is best known for comic roles. But, he tells Gerard Gilbert, he can make an audience believe in him as an Agatha Christie sleuth

When a television drama production crew pitched up on Cromer beach in Norfolk, almost the entire town, it seemed, crowded on to the promenade to watch filming, despite the worsening weather. Even Broadchurch, when that shoots on Dorset's Jurassic Coast, doesn't attract this much interest, and BBC1's Partners In Crime is a new show with as yet no fan base.

Ah, yes, but it does star David Walliams. The 43-year-old comedian, who cross-dressed his way to fame with Matt Lucas in the two-man sketch show Little Britain, has since become a pop-culture phenomenon, with his teasing campness, his marathon charity swims, his bestselling children’s books that have rightly seen him compared to Roald Dahl, and the tabloid-fest about his recently failed marriage to the Dutch supermodel, Lara Stone.

But what has cemented his position atop the often tawdry Mount Olympus of contemporary British celebrity is his role of licensed jester in the court of Simon Cowell; Walliams is the man who puts the brakes on Cowell’s championing of street dancers and boy bands on Britain’s Got Talent and chimes with the public’s taste for eccentric novelty acts. “I’m big in Cromer,” says Walliams, which is a modest way of saying that he is huge everywhere in the UK; his every public step dogged by paparazzi and selfie-hunters. “Everyone… came to watch us, which was fun but surreal because it was like playing to a theatre audience.”

The scene that the locals were agog to witness belongs to a new six-part adaptation of a lesser-known Agatha Christie property, the Tommy and Tuppence stories. Christie wrote only five books featuring these married amateur sleuths, but according to the writer’s grandson, Mathew Prichard, chairman of the company that deals with the business side of the Agatha Christie estate, they were closer to her heart than Poirot or Miss Marple.

“My grandmother was very fond of them,” he says. “They featured in her second book and, 50 years later, in her last book, and… whenever she felt like a rest and losing herself, she returned to Tommy and Tuppence. I think Tuppence shows a remarkable affinity to my grandmother. I can’t really tell about the likeness of Tommy to my grandfather [Archibald] because I never met my him. They got divorced and she remarried in the Thirties.”

The estate recently took over management of the television side of the brand, joining forces with the BBC for the 125th anniversary of Christie’s birth. With ITV’s Poirot, starring David Suchet, ending last year after a quarter of a century, and Miss Marple now being considered for a makeover by the BBC, dramatising the Tommy and Tuppence stories (under the title Partners In Crime ) might seem a canny first move by the author’s estate. However, the idea was entirely Walliams’s.

“I’ve been a fan of Christie ever since I saw Murder On The Orient Express as a kid of about eight,” he says. “I was completely blown away by the story... didn’t see the twist coming. Since then, I’ve read a lot of Christie’s work and have come to realise that these characters haven’t been done for quite a while. There was a TV series in the Eighties [Agatha Christie’s Partners in Crime, starring James Warwick and Francesca Annis] and I thought it was time for a new version. And there was something that really appealed about a husband-and-wife detective duo because I don’t think there’s been one since Hart to Hart [the US TV series with Stefanie Powers and Robert Wagner, which ran from 1979 to 1984]. I like that he has to defer to Tuppence. I think it will have a lot of appeal that the woman is in charge... and she’s more intelligent and heroic than he is.”

Walliams is not only executive producer of Partners In Crime but also one of its two leads – playing Tommy Beresford, an easy-going and none-too successful serial entrepreneur, while Jessica Raine (Call the Midwife, Fortitude) plays his more adventurous wife, Tuppence. I wonder what international audiences – less familiar with Walliams’s persona and drawn to the words Agatha Christie like moths to a flame – will think of his performance. Although he has done Pinter on stage, and Frankie Howerd in the BBC4 biopic Rather You Than Me, on the evidence of the opener of a three-part story based on Christie’s 1922 novel The Secret Adversary, Walliams appears more at ease with the more comic aspects of the role. But I ask how he adapts to the more serious aspects of the drama?

“I’m threatened with my life a few times, and that all had to be as real as possible,” he says. When the heavies are threatening me, the audience has got to believe that too, so I just had to keep that in mind all the time. We didn’t want to be pastiching the Christie world, and so the bad guys really are bad and people do get killed, but there’s humour within the relationship of married people going on this adventure together. We wanted it to be playful and not too heavy, but that goes along with the rest of Christie’s work. If you read the stories, people are killed but people aren’t that sad about it; it’s all ‘let’s find out who killed them’.”

Unlike Christie’s Tommy and Tuppence books, which are spread across the decades, the new BBC series take place in 1952. “She wrote these books from the Twenties to the Seventies,” says Walliams, “and the characters aged throughout the books, and I thought that would be quite tricky to do on television.

“And because in the book of The Secret Adversary, the fear is of the Bolsheviks after the revolution, and of a General Strike, we thought there was an interesting parallel threat in the Fifties, which was the start of the Cold War, and there was fear of Soviet Russia.”

Certainly the Christie estate and the BBC hope to reboot the lucrative literary franchise by making it less predictably cosy and more racy – or, as it’s been described by its director, Edward Hall, and producer, Hilary Bevan Jones, a cross between The Avengers and Indiana Jones. Walliams feels that these adaptations need to rediscover the immediacy of the books.

“They were all written in the present day for Agatha Christie,” he says. “But now they’ve come to mean something else... heritage television... and obviously that has big international appeal because people think of Britain as still being in the Thirties.”