If you’ve been watching Rooster – the Bill Lawrence and Matt Tarses comedy series that just broke a 10-year viewership record as the third most-watched show on HBO Max – then you’ll already know what Phil Dunster is capable of when he gets his teeth into a role.

As Archie, a professor of Russian history at the fictional Ludlow College who leaves his wife for one of his graduate students, Dunster plays a man who is, by his own admission, utterly convinced of his own brilliance. Infuriating, magnetic, “an unbearable narcissist”, and somehow nearly impossible to dismiss. It’s a very particular skill, that, and one that Dunster seems to have been gravitating towards.

“I’ve been told that I have a rather punchable face, so I think that from a purely aesthetic perspective, that may be one of the reasons why I get cast for this sort of characters,” he says. “I’m spending a lot of money on therapy trying to come to terms with that.”

Jokes aside, there’s a real psychological aspect to his craft – and making his onscreen counterparts the least two-dimensional possible and finding out why they are the way they are is where his real work begins. “Trying to find charm in self-aggrandisement and trying to find the brilliance of someone who is effectively a bit of a nightmare makes it so much more interesting.”

To play Archie, or Jamie Tartt in Ted Lasso, you’d think you’d have to be somewhat convinced of your own brilliance yourself. His passion for acting began when he was a teenager at Leighton Park School in Reading. “Drama school legitimised it as a career, because we, somewhat cheekily, were given a degree.”

He was fascinated by the worlds in Alfonso Cuarón’s films – Children Of Men in particular – by Tom Hardy’s transformative performance in Bronson, by Imelda Staunton’s “delusions of grandeur” and ability to pretend to be someone she wasn’t in Joe Orton’s play Entertaining Mr Sloane, which he saw when he was just 16.

Dunster’s first big play Pink Mist, at the Bristol Old Vic, felt incredibly pertinent to his own life, and somewhat familiar. “John Retallack and George Mann [the directors] managed to make it feel like you were just out on a night out with these lads who were describing what was going on around them,” he says. “That sense of ‘we have created this thing together’, and the connection I had with these people, that for me answered the doubt on whether I could go on to be an actor going forward. It felt like being part of something.”

Some of them went on to become really good mates. The kind, he says, that don’t take themselves too seriously, are instinctively loyal and are willing to lead with a vulnerability of some sort.

He’s known his best mate, the producer Patrick Tolan – pictured here, both wearing the latest Mr P. collection – longer than he hasn’t. They now have a production company together, Second Rodeo Films. They’ve lived together; Dunster was the best man at Tolan’s wedding. “We have so much common ground and history. He’s always there and he’s always ready and willing to meet me halfway.”

Letting his guard down is vital to the way he connects, both at work and in private. “Vulnerability is putting yourself in the middle between the two of you and going, ‘I’m a little bit weird, man’.” he says. “Being an actor, I’m not saving lives, but it can be quite a dignified thing to do when you’re putting yourself into a space, often with people you don’t know that well, and you’re just making a strong offer, putting yourself on that line.”

That sense of accountability and having skin in the game feels increasingly central to where Dunster is heading. He’s been cast in the Universal Pictures live-action sequel How To Train Your Dragon 2 (out next year), as Eret, the cocky, self-proclaimed finest dragon trapper alive.

The film is different from everything he’s ever done, but the type of character isn’t far off – and perhaps that’s not a coincidence. “[Eret] is narcissistic but has this fantastic way of seeing the error of his ways and trying to live a better life.” That’s the best part about being the villain.