You may not recognise the rock star Shirley Manson in her first acting role. In episode one of the second series of Terminator: The Sarah Connor Chronicles, the former singer with the multimillion-selling band Garbage has to “play” a gentlemen’s urinal. In episode two, she’s a middle-aged black man. Impressive stuff for a 42-year-old redheaded Scotswoman.

“That’s the genius of special effects!” says a smiling Manson over lunch in a French café in Los Angeles. And, she might add, that’s the bonus of playing a bodymorphing killer robot from the future disguised as a powersuit-wearing CEO.

In the TV spin-off of the big-screen Terminator franchise, Manson plays Catherine Weaver, who appears to be the female boss of the technology company ZeiraCorp. But in reality she’s an advanced-model cyborg – a terminator who can take any human or non-human shape – who has travelled back in time to ensure the development of the computers that will ultimately allow robots to wipe out mankind. Trying to prevent this are Sarah Connor and her son John Connor. Those who have seen James Cameron’s 1991 movie Terminator 2: Judgment Day will remember that John Connor grows up to be the leader of the human resistance fighting the robots in a postapocalyptic world.

In the TV show, which premiered in America in January, Sarah Connor is played by the British actress Lena Headey (star of the blockbusting 300). At the time there was snarky comment in the American press to the effect that TV Sarah’s musculature wasn’t as impressive as movie Sarah’s, the latter portrayed by Linda Hamilton. But there was greater media hubbub around last month’s season two premiere: after Hugh Laurie (star of House), Eddie Izzard and Minnie Driver (The Riches), Anna Friel (Pushing Daisies), Dominic West and Idris Elba (The Wire) and Jonny Lee Miller (Eli Stone), here was another Brit taking an American TV starring gig. And a musician Brit at that. For all the psychodrama of Garbage’s dark pop hits, Manson’s acting CV amounted to a role as the Wicked Witch in a production of The Wizard of Oz at school in Edinburgh.

Manson says that Josh Friedman, the writer of The Sarah Connor Chronicles, called her after seeing a YouTube clip of Garbage in concert. “I was going absolutely bananas,” laughs this famously feisty but thoroughly affable singer. “Somebody had spat on me, and I just lost it. Josh saw me going ballistic, and I think he just thought that I had something deep inside that fitted the kind of character he was trying to cast.”

Manson and Friedman had first come across each other a year or so previously. The singer knew his lawyer wife Christine, whom she had met through their mutual friend Gwen Stefani. Since relocating to America in 1994 to join Garbage, who made four albums before going on “hiatus” at the end of 2005, Manson has become a well connected part of the American musical establishment.

“Josh and I met at Gwen’s baby shower,” Manson says, referring to Stefani’s first child with the British singer Gavin Rossdale. “At the time Josh was developing The Black Dahlia, and we got talking because I’m a huge James Ellroy fan. And over the following year I had lunch with Christine occasionally, and she would jokingly say, ‘Josh has an idea for you to play a terminator in his TV show.’ And I said, ‘Oh, that would be really funny.’ But I didn’t really think much of it.”

In May this year Friedman called and asked her to try out for the role of Weaver. Three auditions and two weeks later Manson was on set, “absolutely terrified” but ready to give it a go. “Over the years I’ve had a lot of opportunities to act, and I’ve always chickened out,” she admits. “Well, mostly because I didn’t really fancy the discomfort of putting myself through the audition process.”

Once Manson had the offer there was no time for nerves. Nor was there time for acting lessons or dialogue coaching. “I just plunged in,” she says. “But I felt as if it was the same with music. When I flew off to join Garbage I didn’t have any training for that either.”

If anything, the flamboyant front-woman used to being a commanding presence in front of thousands of fans is required to underact in the show. When she’s not morphing into killing mode, Weaver speaks in crisp lines, and moves with angular precision. Just the way corporate über-bosses, or sociopathic cyborgs, are meant to.

“I knew that would be to my detriment,” Manson says of her purposefully “stiff” acting. “If I was just a neutral actress coming out of nowhere to be on the show, 99.9 per cent of people would just accept the actress as the character. But when you’re known for something else, people are immediately looking for every flaw and nuance in your performance. I knew that there would be people looking at me going, ‘Well, she’s really stiff!’ But that was a deliberate choice – not to be flamboyant.”

And nothing like a rock star. “No! I had to really focus on trying to keep as still as possible. But I felt she should be weird. She shouldn’t be particularly human.”

But she could be Scottish – like the singer-turned-actor herself, Weaver the future killing machine has a curly Celtic brogue. Manson says that Friedman was happy for her to retain her accent in the drama.

“Well,” Manson smiles, “in the future the robots don’t just take over America – they take over the world. So they could come from anywhere.”

Terminator: The Sarah Connor Chronicles, Wed, Virgin1, 9pm

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