La Roux were on everybody's ones-to-watch list at the beginning of the year, but most of the money was on Little Boots to be the big UK pop story of 2009. Six months on, it's this Brixton retro-synth duo who can claim the third biggest-selling single of the year (In for the Kill), another that beat Michael Jackson to No 1 (Bulletproof), and an album that looks as if it will debut at the top next week.
Elly Jackson, the androgynous 21-year-old frontwoman (Ben Langmaid, the synth-playing other half, doesn't appear on stage), seems to have been as unprepared for this as anyone else. Months ago, Jackson talked up the "massive" live shows she was preparing, but the reality is that this one-off headliner seems to have been put together on the hop: it's nine songs long, devoid of special effects, and gives the distinct impression that Jackson doesn't quite feel comfortable on stage.
Having said that, her entrance is undeniably one of the best of the year. The lights dim, and she is suddenly there on the darkened stage, singing the ghostly "ooohs" that kick off Quicksand. Then a spotlight picks her out, tall and magnificent in white suit and hair that has been tortured into a cascading red ocean wave. It's obvious we're in the presence of a bona fide star. While nothing else has the impact of that icy first moment, the impression of Jackson as something apart lingers.
The next 40 minutes are equally striking, in the sense that La Roux are the only 2009 band whose set could have been transported intact from an early-1980s Top of the Pops. Frigid blue lights, minimalist decor, three shadowy backing musicians standing behind keyboards and syndrums – it's as if the last 25 years never happened. Jackson herself has the futuristic pallor that would have made her an automatic Face magazine cover star in 1982. If only her voice, thin and straining over quacking synths, lived up to the promise of those looks.
La Roux unveil their self-titled debut album, most of which is already familiar to the nearly-full house. Every hissy, trebly tune sounds like a hit, but the two actual hits are fantastic. The whooshing In for the Kill galvanises Jackson; the ice princess melts, and she's shouting the words. Bulletproof, a lament about an anonymous unrequited love, has the same effect. So it's a cautious thumbs-up – and full marks for that hair.
