On an arctic afternoon last winter, I spotted Elly Jackson in west London, looking fantastically sulky. Instantly recognisable, thanks to her gravity-defying ginger quiff, and with managers, publicists and stylists trailing behind her, the singer with the electro duo La Roux — “the red-haired one” — huffed down the street in a pea coat and high heels, looking as if she’d rather be anywhere else but in the situation her then burgeoning fame was placing her. This was long before she emerged as the biggest new British pop star of the year. Six months on, La Roux’s single In for the Kill is an immovable fixture in the charts (it is enjoying its 15th week in the Top 40 and has sold 500,000 copies), and her current single, Bulletproof, went straight in at No 1 last Sunday. Back then, her demeanour was in keeping with a reputation for aloofness and diva strops that earned her nicknames such as Danny La Roux. In fact, Jackson says, she was just cold.

“I can tend to look like I’m about to kill someone,” the 21-year-old says, smiling. “People go, ‘God, you’re moody.’ But I’m not, genuinely. I just frown a lot. I had it at a photoshoot yesterday. They went, ‘You don’t smile much, do you?’ But why do a wacky photoshoot if I’m trying to get across that I’m very, very serious about this? I hate all that ‘I’m a groovy pop star, I’m famous now’. And the more you do things like that, the more people just go, ‘Whatever.’ So now I’ve got this whole thing of, ‘Yeah, she’s really serious, but she’s a moody bitch.’ La Rude and all that stuff.”

Jackson, sitting in a cafe around the corner from the south London house she still shares with her parents, doesn’t say any of this with venom; on the contrary, she laughs far more than she scowls. But you get the sense that her drive and ambition could, without direction, lead her into the most almighty scraps. It comes as no surprise that she found school — or, rather, a succession of them — troublesome. “The teachers just thought I was a stubborn know-it-all,” she says. “No, I just know how I want to do things. Why is that a bad trait? But people don’t see it like that; they see it as cockiness, not as ambition or focus or drive.”

The person who saw beyond the cocksure carapace was the producer Ben Langmaid, a long-term backroom boy in the music industry who has worked with Dido’s brother Rollo and the band Kubb, among others. He was introduced to Jackson four years ago after a friend of his heard her singing and strumming an acoustic guitar at a New Year’s Eve party. Langmaid’s role in La Roux is viewed with suspicion by some: they see him as a string-pulling svengali, a perception that, unfairly and inaccurately, reduces Jackson’s role to that of a blankly reciting puppet. “But that’s what I would think,” Jackson agrees cheerfully. “If I was on the outside, I’d totally think that. I’d read an interview and go, ‘Who is this Ben bloke exactly?’ ” The truth is more interesting, if less shad­owy. Ever since Jackson joined Little Boots and Florence and the Machine in the tips-for-2009 polls, commen­tators have lumped them together, on some occasions seeming to suggest that a blueprint — how to ensure that young female singers, most of them making 1980s- influenced electro-pop, storm the charts — had been drawn up. “I do think some people actually believe that,” Jackson marvels. “My dad said to me this morning that he’d just read something about me being some concept. The most frustrating thing you’ll ever read about yourself is that it’s not you, that it’s all been made up by somebody else. You can’t make up something like this. It’s such a depressing state of affairs.” The search for an inner edit button is almost visible on Jackson’s face. Too late. “I could understand that type of press coverage, maybe up until March. But again, today, there’s something saying ‘How to tell La Roux from Little Boots, Lady Gaga and Ladyhawke’, or something like that. Still — in June? Are they taking the piss? Find something else to write about.”

The emotion with which this is said is in stark contrast to the way that Jackson sings. Detractors have described her voice — a fluting, almost toneless falsetto that can sometimes sound as if it’s attached to the melody by only the thinnest and most threadbare of guy ropes — as cold and off-puttingly disengaged. That is surely missing the point. Langmaid’s most important contribution to La Roux has been to draw a distinction between the strident, even monotonous quality in Jackson’s singing voice and the raw emotion behind the lyrics she writes. That contrast is at the core of electro-pop’s appeal and effectiveness, so it was both natural and skilful to take Jackson’s songs away from their Joni Mitchell-esque origins and locate them within a machine-made functionalism that would both complement and offset their message. On the duo’s self-titled debut album, released last Monday, this results in sonic structures that owe much to the fragile minimalism of early Eurythmics, with Annie Lennox’s restless self-harmonising on Touch a huge influence. Vince Clarke’s work with Depeche Mode, Yazoo and Erasure is another key template. The great joy of the record is the way Langmaid’s brittle arrangements explode suddenly into choruses that burst with colour and passion. There is also a searing emotional directness in the way Jackson documents the decline of a real-life relationship, nowhere more so than in Quicksand’s bleak lines, “Am I your possession? Am I in demand?”.

“There is a big problem at the moment,” the singer says, “in that being emotional is not seen as cool — whatever cool is. But emotions are what songs should be about. And songs are what it all should be about. People assume you love all the other stuff. I had some photographers bugging me the other day. They were, like, ‘Come on, you want to be in the papers, just give us a picture.’ I thought, if I really wanted to give you a picture, would I be shut inside a cab with my coat over my face?”

Jackson grew up witnessing the effects that celebrity can have on privacy — her mother is the actor Trudie Goodwin, who played June Ackland in The Bill — and admits she’s jealous of Langmaid and his anonymity. She acknowledges that her hair doesn’t help. “People look at it,” she sighs, “and go, ‘Novelty.’ But it’s just my hair. If I had things my way, I’d be in the studio 365 days a year. I wasn’t writing songs aged 12 to do all this. I don’t want to do photoshoots and I hate making videos. The end result looks great, but it’s not like that at all; it’s about getting changed in a toilet and getting wee on your socks.” Jackson looks lost in thought for an instant. “Actually, there is a moment in the new video where I smile,” she says triumphantly, then immediately pricks her own bubble. “But only for a second.”

- La Roux is out now on Polydor

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