Bertie Carvel reveals why he almost turned down Doctor Foster

This disconnect is helped by Carvel having shaved off the beard that Simon has. Beyond that, he has an unusual ability to vanish into a character. When he played the cross-dressing part of the terrifying teacher Miss Trunchbull in the musical version of Roald Dahl’s Matilda, he was pleased to win awards but almost more thrilled to receive at the stage door a fan-letter addressed to “Ms Carvel”.

“I took that as a badge of honour,” he says, and such invisibility may be useful at the moment as there are examples of those who play hated characters on screen suffering abuse on the street: “I’m aware that there are people on the internet saying how much they hate Simon Foster. With the millions who watch it, there are likely to be one or two who can’t distinguish between me and the character, and feel a hatred of Simon. So I suppose that puts me at risk.

“And at the level of the really famous actors – which I’m not – that risk is scaled up, and you might be sensible to think about your security. But I’m not paid enough to live in a gated community with private security, and actually I wouldn’t want to live like that. You have to just hope that most people enjoy the fictional reality of Simon without thinking he’s real.”

When I arrive for the interview, the actor is reading Feral, a book by George Monbiot that encourages people to reconnect with their inner wild streak. “I’ve just had my 40th birthday, and two different people gave me Feral as a present.”

Perhaps it was a comment on the characters he plays? “Or maybe it was a comment on my personality,” Carvel laughs.

Certainly, he specialises in protagonists with a feral streak, whom much of the audience is disposed to distrust or dislike: such as Miss Trunchbull, and, on stage at the Duke of York’s, a young Rupert Murdoch in Ink, James Graham’s play about the newspaper tycoon’s launch of The Sun as a tabloid paper in 1969.

With Doctor Foster, does he allow himself to think about the fact that a majority of viewers will despise Simon for the way he behaves? “I was deciding on the bus on the way here whether I’d tell you this,” he teases. “And I will.”

The revelation is that, when writer Mike Bartlett sent Carvel a draft of the opening episode of the first series, the actor was close to rejecting the role: “I had a strong reaction that Simon was such an obviously bad guy, and I felt that was a mistake. I wanted it to be more nuanced, and with a sense of why Simon behaves in that way. I wrote to Mike, and I think, in his own way, he reflected some of that in the rewrites.”

As the show has progressed, Carvel saw himself as the “custodian of Simon”, challenging and arguing about his actions, seeking to understand why he behaves as he does.

Unlike American television, where actors are often asked to commit to up to seven seasons of a series if it becomes a hit, British performers can usually choose whether to return to a role. Did Carvel take persuading to do the second series of Doctor Foster? “Mike came to me on the day he went to the BBC to discuss a possible second series. He actually stopped on the way for breakfast because they needed to know if I’d do it again. And I said yes because I loved the character and the team. There was an element of risk because no scripts were written, but I told Mike the kind of things I’d like to explore.”

Delighted by the show’s ratings, he is more equivocal about some reviews: “A lot of the stuff I’ve read has described the show as a ‘melodrama’, which surprised me. Because to me it feels realistic. Still having some love for someone you hate is entirely recognisable. This primal desire to fight or seduce is often competing with this much more sophisticated side of our brain.

“For example, I think of myself as a quite reasonable, rational, thoughtful, sensitive person and yet, if someone comes and pinches my phone out of my hand and heads down the street, there’s a sudden raging instinct to chase them down and fight them.”

Is that a metaphorical or actual example? “It happened to me a few weeks ago at a bus stop. It was my own fault because I was watching Game of Thrones with bluetooth headphones, and they came up on one of those bikes and grabbed the phone.” Carvel resisted the primal instinct to chase them down and fight them.

“The police were directly opposite, as it happened. When the shock had slightly cleared, I explained that a guy had nicked my phone. And they explained that they couldn’t give chase because that wasn’t what they did in these cases.”

Watching Carvel on screen and stage, I have been struck by the attention he gives to a character’s body language, even to the extent of how they sit down. Simon Foster presides over a table in a brooding, hooded manner that suggests a bird of prey; his Murdoch in Ink slouches, half-reclining at posh restaurant tables in a laid back way that reflects the proprietor’s contempt for English manners.

“There’s a saying, which I think is Oscar Wilde: ‘Give a man a mask and he will show you the truth.’ And that says something to me about acting. I used to worry that, if you were the type of actor who looked different every time, it meant the performance only went skin-deep. Now I think you can transform the outer layer to get at something different inside each time. I really enjoy designing a look for a character,” he says.

“For me, once you’ve got the right clothes and the right moves, something starts to happen that fills in their personality. Often, a member of the audience might say, ‘Oh, I love what you do with your hands there,’ but I’m not thinking, ‘Do that thing with your hands now.’ It’s more mysterious.

“If you look at the analysis of a tennis player, there is a co-ordination of so many things and decisions before the racket hits the ball. And it can’t be conscious because there isn’t time. It comes from instinct and training. And, at its best, that is what acting is like for me.”

Whatever roles he plays in the future (he’s currently working on a TV drama, based on an idea of his own, with James Graham, author of Ink), Carvel would prefer to go on being ignored on the bus and in the supermarket: “I hope that kind of recognition never does happen to me. I keep a low profile. I’m quite cautious about social media. I keep my private life private.”

Whether Carvel might return for a third series as Simon Foster remains off-limits in this interview for reasons of plot protection: “I’d have my balls cut off very quickly by the producers if I told you anything.

“It’s frustrating not to be able to talk about the ending. But I think that what Mike does brilliantly is to play with the audience’s expectations, and have a dialogue with that. If that doesn’t tease too much.”