Andrew Lincoln: 'It's rather exciting playing a policeman who chops up human beings'

If you look through the list of roles Andrew Lincoln has played in his 16-year career, a few trends emerge. He can don the ruffs and toppers and pull off period drama (Bramwell, The Woman in White, The Canterbury Tales), and he is cocksure enough to gaze over the rim of a pint of gassy lager and do young-chap-on-the-cusp-of-stuff (This Life, Human Traffic, Teachers) too. But his latest role, his most internationally successful to date, is a long way from either of those well-worn paths.

As Rick Grimes, Lincoln is a sheriff's deputy from Cynthiana, Kentucky. He has a wife and a son and a police partner. He wears a wide-brimmed sheriff's hat with those funky toggle things on it and he fills a short-sleeve shirt and a pair of figure-hugging "pants" with some style. However, very early on he is badly wounded when an arrest goes wrong and he wakes up a few weeks later in an abandoned hospital with only a padlocked room full of, oh dear, the groaning undead for company.

Within 20 minutes he's swinging a baseball bat at a passing zombie. Later, he hacks one up with an axe. His moral compass begins to whirl like a Sufi mystic, yet this cop-on-the-edge role has made Lincoln the latest British actor to become hugely popular playing an American in America.

"I'm new," he says, pushing a cup of coffee around a boardroom table in a central London office. "That's a big thing for the American psyche. You couldn't have Tom Cruise playing this part – it wouldn't work."

It is quite a leap from being the bloke who secretly fancied Keira Knightley in Love Actually. "Well, yes," he laughs. "There is something rather exciting about playing a policeman who gets to chop up human beings. Take the axe to the small intestine; smear the blood from the chest cavity. Go nuts . . ."

Lincoln is the star of The Walking Dead, which is based on Robert Kirkman's long-running comic book series of the same name. The series inhabits an apocalyptic version of Atlanta, Georgia, one clearly influenced by the work of zombie-movie master George A Romero, but this is a parallel world that has never heard of zombies, much less seen a drooling, ash-coloured corpse stumble noisily down Main Street. No attempt is ever made to explain why this has happened and the "Z" word is never uttered.

These blank-eyed figures are, simply, "walkers" and the first few survivors he meets have no idea who, if anyone, is still alive.

"We're all coming to terms with the idea that this is it," Lincoln says. "No planes are coming to rescue us. There's nothing out there. As far as we know."

What's surprising is how rich and cinematic the series is. The concept is as old as the hills, but here it works brilliantly. British actor Lennie James plays a dad whose wife is now among the shuffling hordes. He is willing to pick up a shotgun and take out any number of others, but when she is in the crosshairs he just can't pull the trigger, despite knowing there is no way of rescuing her and that she would kill him and their son as soon as look at them.

The show's success has meant that, some months after it was first screened, and just before he heads back to the US to start filming season two, Lincoln – who has signed up for six more years – is still "selling" it. Only now he's meant to know everything about how US TV works.

"And I don't," he admits. "I spend my working life pretending to be someone else. It's annoying in the way I'd like to be doing something else, but after 16 years of working this is like starting over in a whole new industry. What I do know is the next thing I do must be completely different and absolutely great."

So when we see him bashing up a moaner in another zombie series in two years' time, we'll know it's all he's been offered?

"Exactly!" he says, lifting his coffee. "But hopefully that won't happen."