Andrew Lincoln is eyeing me narrowly. I know that look. It’s the one he has been using for the past six years in the hit US post-apocalyptic TV drama The Walking Dead, before upping the body count. His character, Georgia sheriff Rick Grimes, has macheted, axed, gunned and spiked at least 150 zombies and quite a few humans since the show’s premiere in 2010.

In Britain, Lincoln may still be best known for his performance 20 years ago as lovable loser Edgar “Egg” Cook on BBC2’s then hipster drama This Life, about five twentysomethings trying to cut it in the legal profession. Stateside, though, he is renowned as the go-to guy to take out the undead trash – 14.6 million Americans watched the season six premiere last month. He is the Englishman who slayed America.

So, why the zombie death stare? It’s because I ask him about politics, a subject that sends him scampering off in the opposite direction, as if pursued by an implacable, if slow-moving zombie horde. Interviewing celebrities is often like this.

But surely The Walking Dead is richly allegorical, I suggest. The refugee crisis, resentment over immigration, Islamophobia, distrust of government – all have their onscreen parallels in the show that has made Lincoln globally famous. And Trump’s foreign-policy platform – building a wall to keep out Mexicans and refusing Muslims entry to the US – finds its parallel in The Walking Dead, in which humans build walls to keep out the undead? “I’d rather not be drawn into saying something about Donald Trump,” he says. Disappointing.

In any case, Lincoln argues, The Walking Dead is bigger than mere presidential elections. “In western culture, we have ignored death. We’re running the other way – everything is about life and youth. So, there’s something resonant about walking around with our own death masks. Zombies are the visible embodiment of death staring at us with our own faces.”

True, those death masks are made to order in a studio in California and shipped in their thousands to the set in Georgia each season to be worn by heavily madeup extras, but let’s not spoil the story.

Lincoln as Rick Grimes with Danai Gurira as Michonne in episode one of the new series of The Walking Dead. Photograph: Gene Page/AMC

“We’ve got an opportunity in this crazy-ass world we’ve invented – which is obviously very cool ass, bad ass, thrilling exciting, bloody, gory, scary and action-packed – to say something about what it is to be human. It’s about the undead, but it’s also about what it is to be alive.”

Asses notwithstanding, Lincoln speaks in a posh English accent, which is discombobulating, because for eight months of the year, during filming of The Walking Dead, he speaks in an American Southern accent on-set, off-set and at home in Atlanta, Georgia. Maybe his pillow talk is that of a Southern gent – he won’t let on.

“My wife and children think I’m bananas. They’re like: ‘Please stop doing that.’ It’s very unsettling for them because they don’t know who they’re talking to.” Don’t his kids speak American at school in Atlanta? “No, they’re Brits, because they like the cachet of it. As soon as they start to get a bit of an American twang, we pull them out and then we put them back in over here.”

When he flies home to Wiltshire each year, though, he undergoes a transformation akin to what happens when a murdered human regenerates as a zombie: Andrew Lincoln becomes Andrew Clutterbuck.

Born to a South African nurse and a English civil engineer in 1973, young Andrew was told to ditch Clutterbuck by his first agent, because it made him sound like a hobbit. Advice that, given the Postlethwaites, Cumberbatches, Spalls and Broadbents who bespangle the Brit thesp firmament, seems dubious. But still, he tells me, the identity change is useful for him to guard his privacy. Even his credit card reads Clutterbuck.

Twenty years ago, only one year out of Rada, Lincoln was made when he got his big break on This Life. “There are certain roles in my career that make you scream out loud,” he says. “That was the first without a doubt.”

On one of the first days of filming, he was required to come out of a shower and get it on with his screen wife, Milly (Amita Dhiri). “I was really committed and everybody was really in the zone. But the shower was cold. And I was doing it wrong.

“The director came up to me after the first take very respectfully and said: ‘It’s like you’re in Ballet Rambert trying to dance to get the towel. Can you just get out of the shower normally?’” The scene impressed his mates, but for the wrong reasons: “A buddy in Bath texted me and said: ‘Just watched the episode with you and Amita. That’s one of the best lesbian shower scenes I have had the privilege of witnessing.’”

Did he like Egg? For all that the character fails as lawyer and cafe owner (and supports Manchester United)? “I love him! He was a sweet-natured guy and he spoke to a lot of people who had come out of university and were stuck in a rut and were re-evaluating what they wanted to do and believed in.”

Daniela Nardini as Anna, Amita Dhiri as Milly, Andrew Lincoln as Egg, Jack Davenport as Miles and Raymond Tikaram as Ferdy in This Life. Photograph: BBC

According to Lincoln, when the actors hung out together off-set, they couldn’t quite forget the roles they were playing: “We used to socialise a lot, as we were filming as a gang. Everybody would come up to me at nightclubs because they liked Egg and they hated Jack [Davenport, who played Miles, the posh twerp with a calamitous sex life]. They thought he was a dick. Jack was like: ‘What’s going on? I’m really a nice guy.’”

The 2007 This Life reunion show, in which Egg became, to my mind, an unacceptably successful and smug novelist, bombed. (“Maybe it would have been better to leave Anna, Egg, Miles, Milly and Warren in their graves,” wrote the Guardian’s Sam Wollaston at the time.) “I don’t necessarily read critiques and I don’t judge that as a reason not to see it,” he says. “I mean, it was very nice to see everybody, but I’m not sure we’ll be doing it again.”

Nonetheless, the series gave Lincoln’s career a massive boost. “It gave us leverage and notoriety and access to meetings. It also gave me two years’ experience in front of camera after three years’ theatre training. It made me understand why there are so many people on set, looking at you and touching you.” Touching you? “People are always invading your personal space on set, especially on The Walking Dead.” They’re forever smearing him with zombie viscera, he explains.

I glance sidelong at this London-born, Bath-raised, Rada-trained actor, looking fruitlessly for the ghost of Edgar “Egg” Cook. How did this genial 42-year-old, who today looks good carrying off designer stubble and even a mini-mullet without it going early Michael Bolton, get to be the face of one of the millennium’s most successful US dramas?

Until 2010, after all, his CV was crammed with unremittingly British stuff – not just This Life, but probationary teacher Simon Casey in C4’s 00s dramedy Teachers, and turns in Britflicks such as Richard Curtis’s Love Actually and Made in Dagenham. How did his career switch so dramatically? Lincoln says he was lucky enough to look haggard after the recent birth of his second kid when he auditioned for the role of Rick Grimes. “I hadn’t slept for three days, and I was shell shocked. I had this apocalyptic chic that probably fitted the bill. I looked like I’d survived a zombie apocalypse.”

Frank [Darabont, show creator and director of The Shawshank Redemption and Green Mile] wanted the Gary Cooper of High Noon, a classical leading man, very moral, almost gentle and quiet. But he also wanted a family man, so the perfect storm of meeting someone who had just had his second child was really appealing to him.”

When he got the part, Lincoln signed away a chunk of his life. “You have to sign a standard Hollywood contract of five or six years. Generally, a show doesn’t go past one season, so it is a matter of hedging your bets. But we [he and his wife Gael Anderson, daughter of Jethro Tull frontman Ian Anderson] did have that conversation while our child was screaming during a night feed, and decided to risk it.”

“I’ve always wanted to work in America because of those brilliant east-coast political movies of the 70s and 80s – great scripts, wonderful performances, gritty urban parable.” He cites Serpico, The Conversation, The French Connection and the Godfather trilogy. “Whenever I’m losing faith in the planet I’ll get a box set out and watch those.”

It was one of his co-stars on This Life who lured him over to give it a go. “Jack was one of the main instruments in making me go to America. He said: ‘Come over here. The water’s warm.’”

As a result, Lincoln has become part of a successful British invasion of American TV, joining Matthew Rhys (The Americans), Dominic West and Idris Elba (The Wire), Ruth Wilson (The Affair), Michael Sheen (Masters of Sex), Martin Freeman (Fargo), Damian Lewis (Homeland), not to mention Lennie James and David Morrissey, his fellow Brits on The Walking Dead.

None of his compatriots, though, manage to go quite as nuts on screen as Lincoln. In a recent episode, Grimes – understandably vexed after his girlfriend and her son are eaten by zombies, and his son has his eye put out in a shooting accident – picks up an axe to vent his spleen on the milling zombie hordes. Does he really go nuts or is the scene so choreographed that he has to be controlled? “Oh, I’m going nuts. Don’t worry about that. I’m employed to go into a zombie frenzy killing spree. That’s what I do.

“It is choreographed, of course, because otherwise we would have a lot of insurance problems. We’re very fortunate that we have a lot of committed, hardcore stunt zombies.”

But what does Lincoln know? He has never seen the show. “I haven’t watched myself for 15 years, because I don’t enjoy it. There’s a lot of working parts that can change your performance in between you giving it and it going out. I just realised I’d prefer to have my own imagination about what the story is.”

Lincoln as Rick Grimes with Chandler Riggs as Carl Grimes in The Walking Dead. Photograph: Gene Page/AMC/AMC/Lionsgate

If he had seen the results of his work, he might share the worries of some critics. Rick Grimes, they fear, has become less Gary Cooper and more a tooled-up nutjob devoid of a moral compass – perhaps even the show’s villain – rumoured on fan sites to be facing termination. Lincoln won’t comment on whether Grimes is going to be written out, but in any event he is now plotting his exit strategy from the show. Like anyone spearheading a lucrative franchise – think Craig as Bond, Spacey as President Underwood, Clarkson on Top Gear — he risks getting typecast and becoming frustrated.

“The fun of my job is I get to dress up for a living and play different people,” he says. That dream has been thwarted because of commitments to the show. “The window of opportunity is so small. I was going to do a play and it would have meant me getting off a plane from America and going straight to rehearsals, doing the play, getting back on plane and going straight back to America. I couldn’t do that. My No 1 responsibility when I’m not slaying zombies is being a parent.”

What does his wife do while he is taking out the zombie trash? “Everything. She’s the reason I’m able to do this mad job. She has built a life in Atlanta while I’m away filming. I don’t have a smartphone or apps or anything and people ask me why. I say: ‘My wife is my app.’ She’s magnificent. She’s in the most honourable profession in the world – she’s a full-time mum.” He glances at the female PR across the room for approbation and says unexpectedly: “Fight the power!” Quite so, although if I compared my wife to an app, I’d be sleeping on the sofa tonight.

Lincoln doesn’t do social media either. To keep the madding crowds of fans at bay? “I’ve got nothing to say and I’m just too busy. But I don’t get it – people taking photos of their own food? That’s very odd behaviour.” The PR woman gently objects that she does just that. “Oh God! That’s why I’m not on social media – straight away you’ve isolated half the world!”

Does Andrew Lincoln have what it takes to survive a zombie apocalypse? I get the zombie death stare for one last time, before he cracks a smile. “I think my wife is the one who would get me through, probably. If I did survive, it would only be due to her incredible dexterity in all things.” Onscreen, Andrew Lincoln may be a buff, zombie-slaying post-apocalyptic survivor; offscreen, he’s as helpless as a kitten up a tree.

The Walking Dead is on Mondays at 9pm on Fox