Gough has done film (Colette, The Kid Who Would Be King) and television (a Bafta-nominated role in Too Close) before, but Andor is a bigger and stranger proposition. First there is the secrecy that surrounds all Star Wars projects. We spoke last year, when she had signed up for the series but was contractually obliged to say no more. “There’s a red dot on my head,” she said. “There are people in the park ready to shoot me.”

Now she is negotiating the equally unfamiliar experience of a Disney junket. Strikingly chic in a black trouser suit, Gough has been led by a publicist into a suite at the swish Corinthia hotel near Charing Cross. “This is insanity,” she says. “I’m here staying in a really nice room. When I got off the plane, there’s two people there and their job was to get me into the car. They said, ‘Oh, I can see why you’d lose sight of what’s real.’ ”

It would be a tragedy if Gough turned into one of those pampered stars, trotting out banal answers in airless rooms. It seems highly unlikely, though — her sense of the ridiculous is too strong. It helps, she thinks, that she has come to mass entertainment quite late. “If it had happened at 22 . . . 42, not so bad.” It was a hard decision, she says. The immediacy of theatre makes it “so much easier, and I get a clap at the end”.

The last time we spoke she talked about being cast in a Game of Thrones prequel and justifying it to herself: “The part is great. And there are good people in it. And I want to buy a house.” That show ended up being cancelled before it aired. “I was, like, ‘I’m good. I’m not meant to be in a franchise,’ ” she says. “And then Star Wars rang. And I was, like, ‘Really? So I’m not going to do that franchise — I’m going to do the biggest franchise in history.’ ”

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Not that she’s a fangirl. “It’s my first real experience of Star Wars,” she says, even though it was around in her childhood “because I’ve got five brothers”. Gough was born in Co Clare, the seventh of 11 children to an electrician father and a mother who had her hands full. While the Force was strong with her brothers, Gough was “obsessively into Batman”.

When she was cast in Andor she watched Rogue One, in which Andor and his fellow rebels steal the plans for the Death Star. She was impressed, but still worried that the new series would be a game of silly space lasers, and asked Gilroy to see the top-secret script. “It didn’t feel like I was reading a Star Wars script — it was just character-based stories.” There was a scene in which Dedra is “sort of humiliated and has to stop herself from crying. And I thought, ‘I really relate to this. But it’s in space.’ ”

The costumes, conversely, were reassuringly larger than life. Dedra is a vision of totalitarian power-dressing: cream tunic, knee boots, severe blonde bun. “Taking over the world through tailoring,” Gough says with a chuckle. Yet there were limits to her sartorial ambition, as she discovered when she tried to open the top button of her tunic. “I wanted to do a stayed-up-all-night-working thing. Everything stopped and it went up the line and then it came back that nobody has ever opened the collar.” Disney said no. “Tony calls them the Vatican.”

A big draw was that the plummy-voiced Dedra was on the dark side, she says. “And unapologetically so — it’s not like she’s gonna fall in love and move to the Star Wars suburbs.” There aren’t many female Imperials — she can only think of her friend Indira Varma in Obi-Wan Kenobi and Gwendoline Christie in The Force Awakens. “It is a great thing, initially, to see a woman in this uniform. But then we all get over that because the fact is that she’s a fascist.”

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One touchstone for the character was Gustavo Fring, the drug lord in Breaking Bad. Gough remembers a scene: “There’s a guy making an excuse for something he’s done. And Gustavo the whole time is just taking his suit jacket off. Everything is meticulous and completely silent. And then he does this heinous thing, washes his hands and puts everything back perfectly.” That, she thinks, is Dedra to a tee.

She had to dial down her theatrical exaggeration, though. “I came in and everything was, like, ‘I’ve got a gun and I’ve got a coat.’” The director, Ben Caron, showed her the scene on a monitor. “And I thought, ‘The more she moves, the more power she loses.’ He said, ‘Just put your hands behind your back.’ ” The result is a study in contained evil.

Gough is starting to realise “how big this is” but at least she is prepared. “When People, Places and Things became a hit my initial response was aggression: ‘What do you want from me?’ It took me a while to go, ‘It’s a nice thing.’ ” She doesn’t talk about her love life but happily chats about moving from Hackney in east London to Notting Hill in the west to make the commute to Pinewood Studios easier. Once the second season of Andor is done she will go back to Hackney.

Gone are the days when she worked as a waitress, childcare assistant and even stand-up comedian to pay the rent and took any acting job offered — “second prostitute on the right, who’s gonna get shot in the head”. Now it’s prestige projects all the way, from Under the Banner of Heaven, a recent mini-series about a Mormon murder co-starring Andrew Garfield, to Palomino, a forthcoming crime series set in Spain for Netflix.

“I come in and do a few episodes of baddie acting,” Gough says of the latter with a smile. “I think that’s where I’m headed, into years and years of plausible baddies. And then I’ll go to the stage to do mothers and wives and things.” It’s an absurdly modest way to talk about such an exciting career, but it’s heartening too. There’s no danger of Gough losing sight of what’s real. Andor starts on Disney+ on September 21