Lily Allen, Academy Bristol <br/> Basement Jaxx, Koko, London

It takes a lot of effort to appear effortless. Lily Allen's MySpace-assisted rise to becoming 2006's breakthrough pop act may have had a devil-may-care air of "Oh, am I famous, then? Well, I'm not bovvered either way, really..." about it, but beneath the surface, make no mistake, those swan-legs have been paddling themselves into a blur.

Behind every "internet phenomenon", you can bet your bottom quid there's a squadron of whey-faced corporate minions, robotically clicking "Add Friend" into the wee small hours. Which is why, when Allen slags off fellow net-worker Sandi Thom, there's a degree to which the lady doth protest too much.

That said, Allen's internet presence has at least been an entertaining one. In addition to the egregious Thom, Allen - a self-proclaimed "gobby bitch" - could always be relied upon to cheerfully slaughter her fellow pop stars via her blog (from Kylie to The Kooks, from Carl Barat to Paris Hilton). In an airbrushed era of false mateyness and dull diplomacy, Allen's unschooled lack of tact is refreshing to those of us who remember when that kind of thing was the norm, not the exception.

Nor is she coy about admitting she's a drug-using party animal. This apparent unaffectedness - a carefully focus-grouped affectation though it may well be - has undeniably chimed with a certain mood among a certain generation, who neither know nor care who her famous dad is. (She's at pains to downplay her trustafarian, celebrity daughter status, recently insisting in The Sun that she spent her childhood in a council house and ate spaghetti on toast.)

A couple of thousand delegates of said generation are packed into the Academy tonight, hanging on (and chanting back) her every word. Lily Allen is the poster girl for the New Informality: breezily nonchalant, pointedly refusing to take this pop music thing, or indeed anything, too seriously, because it's only a larf, innit?

Poster girl she may be, but she's nobody's idea of a classic pin-up. Lily Allen looks like a foetus, albeit a pretty one, and she scrubs up nicely in her false eyelashes and big Sixties hairdo, flouncing around the stage in her big glittery wedding cake of a ballgown, acting more like a tipsy stage invader rather than the main attraction.

Her band, assisted by a parping horn section, recreate the sample-heavy sound of her album Alright, Still live, and summery reggae and downtempo ska is clearly this skankin' queen's favourite musical flavour (you just know that "Ghost Town" and "The Tide is High" got a lot of plays in her house when she was a kid).

Lyrically, though, her abilities have been overstated. Too many people have been wetting themselves about that heavily signposted "Tesco/al fresco" rhyme, and giving Allen plaudits simply for writing about recognisably real British life at all. She is, of course, far from the only current artist to be doing this (Jamie T, The Rakes, Plan B, The Streets), although probably the leading female in the field (give or take the odd Lady Sov or Dynamite-ee-ee).

My favourite moment, in fact, isn't an Allen song at all: she does wonderful things to Keane's "Everybody's Changing", reinventing it in a Studio One style. It's the sort of thing which used to happen in the Seventies - singers like Susan Cadogan immediately recording reggae covers of the hits of the day - and it's the reason why so many of those Trojan box sets are such a joy.

Lily Allen herself? Oh, she's still an irritant. But it's in such a way that you kind of enjoy being irritated.

The idea of an enjoyable irritant is key to Basement Jaxx right now: the scratching dog on the cover of their latest album, Crazy Itch Radio, looks like he's having a whale of a time.

Basement Jaxx (left), one of a handful of dance acts to have attained longevity and elevated themselves to arena-filling status, know what they're there for. Felix Buxton and Simon Ratcliffe understand that their role isn't to innovate. Leave that to the solemn head-nodders and Wire magazine readers. When the two life-loving singers romp out to front a version of "Red Alert" which re-uses Chicago's "Streetplayer" sample from The Bucketheads' "Da Bomb", it's clear that the Jaxx still realise that it's their liberty, nay duty, to steal from promiscuous sources, be they avant-garde or traditional, and turn the spoils into great pop.

This BBC Electric Proms show isn't the slickest I've seen from BJ. There's no light show to speak of, and there are uncomfortably long pauses between songs, in which they uncertainly ask "How you doing, London?" (always a poor thing to ask a crowd).

It does, however, provide a chance for Jaxx and their repertory of guest singers to showcase the super-eclectic sound of Crazy Itch Radio, from the Russian accordionist on "Hey U" through the showbiz razzmatazz of "Do Your Thing" to the Ray Charles style blues of "On the Train", essentially a solo number for jazz singer and organist Tommy Blaize.

The album's - and show's - highlight is current single "Take Me Back to Your House", featuring Martina Sorbara of excellent Canadian synthpop duo Dragonette (wearing impossibly tight gold leggings and what looks like a metallic emu on her right shoulder), which literally spans the continent of Europe, combining Spanish flamenco with Jewish klezmer.

The oldies, though, prove most popular, notably "Jump & Shout", featuring a mad high-speed MC in African robes with a cape made from the British and Jamaican flags, and the glorious "Good Luck", proving that vengeance is both a dish best served cold, and an itch that sometimes you can scratch.

s.price@independent.co.uk