Approaching 50, the <i>Alien: Covenant</i> star is fitter, happier and as in demand as actors half his age. How did he do that? .

Mr Billy Crudup is a director’s actor, the kind they like to damn with faint praise. Here’s Mr Cameron Crowe, the rock critic-turned-filmmaker who had him play mythical 1970s rocker Russell Hammond in 2000’s cult film Almost Famous: “When Billy makes it, it’ll be kind of an accident.”

Here’s Chilean auteur Mr Pablo Larraín, who made Mr Crudup the antagonist in last year’s Jackie, casting him as the journalist foil to Ms Natalie Portman’s grieving Ms Jackie Kennedy: “[Billy is] someone who’s very hard to grab and say exactly who he is.”

But within that “faint” praise lies a world of respect, and acknowledgement of Mr Crudup’s singular approach. In fact, as his half-century looms, that elusiveness-slash-unwillingness to be a star is serving the man very well indeed.

He’s the captain of the ill-fated expedition in Sir Ridley Scott’s latest Alien film, Alien: Covenant. He’s the leading man in Netflix’s next blue-chip series, the psychological thriller Gypsy, playing the husband of a therapist portrayed by Ms Naomi Watts. The 48-year-old has also just been cast as the male lead in the next film from Mr Richard “Boyhood” Linklater, an adaptation of best-selling novel Where’d You Go, Bernadette?, opposite Ms Cate Blanchett.

And finally – as seems mandatory for any actor worth their CGI salt – the Texas- and Florida-raised, New York-based actor has booked his spot in the comic-book multiverse. Crudup plays the father of The Flash, a portrayal that has earned him a re-teaming with his Watchmen director, Mr Zack Snyder, in the upcoming Justice League.

So, Mr Crudup: your career-long aspiration to be a character actor has finally paid off. How do you feel?

“I’d love to say it was my masterplan,” he says, “and that I thought it would happen a lot sooner.” Radiating energy, sat in a central London hotel suite, Mr Crudup is crisply attired in white shirt, grey trousers and smart Italian shoes.

“The fact of the matter is, no. I’ve had phenomenal opportunities for a long time. It hasn’t always been in things that people have seen. Because it’s a collaborative art form – you can have good intentions and still make a big piece of shit!” Mr Crudup notes with a cheerful honesty that, it’s soon apparent, is something of a default setting.

Thus, he sought out challenging roles to wrench him out of his comfort zone. For example: he appeared in a 2013 Broadway production of Mr Harold Pinter’s No Man’s Land. As he told an American interviewer at the time, it was finally an opportunity “to do a character that I had always wanted to do: an east London thug”. Was he being serious?

“I was!” he says with a hand clap. “I didn’t know if I could do it – I’m suburban American, upper-middle-class, with a good education… But that’s what’s so fascinating about Pinter as a playwright: he gives the performer an opportunity to create the tension themselves without saying anything. That’s something I relish. Making someone dangerous because of what they don’t say is something that was of interest to me.”

Meanwhile, back at the multiplex, in the second of Sir Ridley’s prequels to Alien – the follow-up to 2012’s Prometheus – the actor plays Captain Oram alongside Mr Michael Fassbender, who returns as a high-functioning android.

But it’s Mr Crudup who’s in charge, piloting a corporate, deep-space expedition packed with sleeping colonists. Their destination: a new, Earth-like planet. Their problem: an odd, human signal emitting from somewhere on their flight plan. With a beatific smile, Oram bats away the objections of his second-in-command and decides that they should investigate. Mr Crudup admits that, initially, Sir Ridley only supplied a broad idea for the character: “I think he’s a religious zealot.”

In the film there’s only the briefest line of dialogue hinting at Oram’s backstory: “I saw the devil in my childhood…”

“Right,” he nods, “and that’s never explained. That was a feature of Ridley and [scriptwriter] John Logan imagining that he had a kind of punitive Pentecostal upbringing – people beat the shit out of him. You know, I can remember that my dad would go to church because I think his mom wanted him to go. He would talk about ‘the man upstairs’ and dress super-sharp for church – but he was also a bookie and a loan shark and stole shit! That’s my dad!” he laughs.

Mr Crudup’s parents split up when he was young, and he and his brothers moved from New York to Texas, and then to Florida. He acted while at university in North Carolina, before taking an acting degree at NYU’s Tisch School of the Arts. He landed his first film role two years later, in 1996’s Sleepers, and hasn’t stopped working since.

As to why he’s joined a 40-year-old franchise that’s half-a-dozen films in, the first of which came out in 1979, when he was 11, he has a simple explanation: the first Alien movie.

“Dude, that scarred me! When I saw that little thing, all bloody and popping out of John Hurt’s chest, going ‘mee mee’ and scurrying across the floor – all of us in school were like, ‘What the fuck was that?’”

I tell him, so the story goes, Sir Ridley didn’t tell any of the rest of the cast on set what was about to happen.

“Oh, really? He’s so naughty! He’s like a 13-year-old – with a cigar! He understands cinema in a pretty extraordinary way, but he gets so giddy about it. There was this decapitated head on one of the sets, a perfect rendering of this girl’s head. And he beckons me over: ‘Billy, come take a look at this. Disgusting, right? It’s beautiful.’ And that giddy enthusiasm is really infectious.”

Sir Ridley, he reports, likes in-camera effects: real spaceships, real landing craft and, “when the aliens started to arrive, he had people in costumes chasing us. Dude, they were full-on gymnasts and contortionists! The scene where I kill the alien? That guy is 6ft 8in, had on that alien mask, and the hands, and that mouth – there was no imagining I had to do. It was horrifying.”

Watchmen, he adds, “was completely different”. In Mr Synder’s misunderstood 2009 adaptation of comic genius Mr Alan Moore’s graphic novel, 5ft 8in Mr Crudup was cast as Doctor Manhattan, a scientist turned into a blue post-human god after getting caught in an experiment gone awry.

“Trying to play the Master of the Universe when you’re in PJs that are riding down your ass because they’ve got 50lb battery packs in them, and you’re wearing lifts so you can look 6ft 4in, and your fellow actors are laughing at you – that,” he chuckles again, “takes some imagination.”

For all his relatively compact stature, and as much as he touches repeatedly on his advancing years, it doesn’t take much to see Mr Crudup as a deep-space leader of men, Master of the Universe or, indeed, dad of The Flash. He looks in great shape.

“I appreciate that,” he beams. “I’ve had a lot of work done!”

The truth is more prosaic, and, appropriately for this below-the-radar actor, less Hollywood. “I grew up with two brothers. And we played all sports, but I was the shortest kid in my class – and that skinny. So in high school, about the only thing that suited me was wrestling, because you had to wrestle somebody in your weight class.

“And I wasn’t very good,” he says. “The year that I didn’t wrestle, we won [the] state [championship], which gives you some idea of how helpful I was to the team. But in any case, I’ve always been physically active. And when I became an actor, running became a big thing for me. I liked running for the psychological ‘release’. I really needed that: there’s a lot of pressure in acting, it’s up and down, sometimes you’re on top of the world, sometimes people are shitting all over you, it’s hard to maintain all of your relationships…”

Mr Crudup is perhaps referring, however obliquely, to the period in 2003 when he broke up with his pregnant actress girlfriend, Ms Mary-Louise Parker, and embarked on a new relationship with actress Ms Claire Danes, latterly of Homeland fame. The tabloid coverage was merciless. It’s not a period he likes dwelling on, understandably – as he recently said: “There are other people involved. Why get into a public discourse when you’re still trying to work it out?”

Five years ago, Mr Crudup broke his toe and had to stop running. He visited a gym, Drive 495, near his home in New York’s SoHo, and approached trainer/owner Mr Don Saladino for advice. Ever since, Mr Crudup has hit the gym three or four times a week, putting himself at the mercy of Mr Saladino’s team. “What do I do? Whatever they tell me. It’s usually circuits of three – plank for a minute, rows or presses or squats – a lot of ass work. Then you do some cardio, which might be rope-work. But it’s all interval work – 10 seconds hard… a lot of rotational stuff… and I play a lot of golf.”

He plays off a handicap of five – an impressive number, but not one, let’s be clear, he’s attained through underemployment. “It’s because I’ve been playing since I was kid. Where my grandparents lived, there were a lot of golf courses, so we’d sneak out. And again, my brothers and I were competitive as shit.”

But he’s no teetotal health freak. He likes a beer.

“It was funny, last night I went to a pub down just the street from here – I had two pints of beer and I was shit-faced! It’s so different from American beer! That’s what I like about Corona – you don’t get bombed.

“But, no. I try to eat healthy. As I tell my son,” he says of Mr William Parker, now 13, “I’m for moderation. Just try to find a little of everything and you’ll be fine. I’m not into the new diet with probiotics and you can only eat spinach on Wednesdays at a temperature of 110ºF,” Mr Crudup says. He says he is a homebody, and he concedes, currently single. Happily so?

“Happily,” he begins. “Well, no! My son is with me part-time, so if I’m not working, I’m with him. And I have a great group of friends in New York. But I’m happiest when I’m in a relationship, for sure. And I have great faith that I’m going to find one to persevere with.”

Mr Billy Crudup, it’s clear, is supremely comfortable in his own skin. He’s landing the parts he wants, in the projects he wants. Better still, his back catalogue is the gift that keeps on giving. Watchmen is emerging from the overhype that attended its release and being reappraised as one of the boldest, most thoughtful superhero – or, anti-superhero – movies made. And as for his take on Almost Famous’ Mr Robert Plant-like rocker Russell, who shouts “I am the golden god,” before launching himself off a rooftop into a swimming pool…

“I get more comments on Almost Famous now than I ever did when it came out, for sure. And it’s a much younger crowd – 20-year-olds. But they still end up [saying], ‘Well, you’re still my golden god… even if you’re in your golden years!”

There he goes again with the age thing. Mr Crudup is hitting 50 next summer. How is he feeling about that?

“I said to my friend the other day, I feel like my fifties are when I’m going to really shine,” he says, not entirely seriously, but not entirely joking either. “I’ve just been working up to becoming a halfway normal human being. My fifties are going to be when I finally get it down.

“So,” he beams with a final delighted flourish, “see you in rehab!”

Gypsy is on Netflix from 30 June