Saint Etienne, Barbican, London <!-- none onestar twostar threestar fivestar -->

On an Indian summer's evening in London, one of the capital's most loved bands give us something special. Saint Etienne helped set the template for Britpop in the early Nineties, reintroducing the colloquial culture of cafés and cups of tea to the charts, invoking an affectionate greasy-spoon bohemia. Their landmark 1991 debut Foxbase Alpha married dance music to wistful pop, though their magpie attitude since, absorbing everything from Brian Wilson to electronica, has gradually eroded their mainstream fame.

This is an ambitious evening. First they perform their soundtrack to a new, Barbican-commissioned film, as it screens, then they play their new concept album about a London tower block, Tales from Turnpike House. It shows that Saint Etienne are still a force to be reckoned with.

The film, What Have You Done Today Mervyn Day?, is the group's second collaboration with the director Paul Kelly, after the London elegy Finisterre. Concentrating on the Lea Valley, the east-London ghostland of derelict industrial estates that once dealt in plastic, petrol and printing, through which a teenage paperboy dreamily wanders, Mervyn Day? is potently evocative. Like an Iain Sinclair book, we see ugly, ordinary London through Kelly's eyes, until its strange beauty begins to surface.

It is set on 7 July, the day after the Olympic announcement that will mean development erasing this zone. Radio-news fragments about the London bombings serve as an evil counterpoint. To this visual hymn to the dream-London of their songs, Saint Etienne add melancholy flutes, guitar pulses and choral harmonies. It's a triumphant cross-media performance. At its finish, the band are cheered as if they've played their greatest hits. The piece's impact is proven at the interval bar, where everyone talks urgently about their own slice of London. A primal sense of place has been awoken.

The singer, Sarah Cracknell, takes centre-stage next. Girlishly glamorous in a spangly top, she's a gawky dancer and a breezy singer, embodying the band's amateur enthusiasm. The musical masterminds Bob Stanley and Pete Wiggs stay modestly behind her on keyboards. Long past the success and fame which briefly brushed them, they look like loyal old friends now, in it for the long haul.

The audience, too, approaching middle age and standing up to dance in scattered knots, have lived with the band since they were young, deepening the affection that hangs in the air tonight. The Turnpike House song "Teenage Winter", a ballad about ennui and frozen hopes, seems to speak to them directly. "Side Streets", by contrast, reminds us all of careless youthful pleasures, and the dangers that can haunt them in a city. "Got cash in my pocket to last the weekend," Cracknell sighs, over a hazy beat. "Got features I don't mind, and would quite like keeping..."

The beautiful "Milk Bottle Symphony", describing the murmur of music as a tower block's various inhabitants start their day, then gives romance to every sort of life, dead-end or not. It's strange to think that the music press used to attack Saint Etienne for their supposed irony, when they offer a song that is so intensely moving. The Arabic-tinged glitter-disco of "Lightning Strikes Twice", and the liquid synths and Led-Zep bass of "Last Orders for Gary Stead", continue a career of genre-fusing.

The new single, "A Good Thing", then returns the band lyrically to those mornings in the greasy spoon. The encore, when they briefly dip into their past, adds a finishing touch.

On "Nothing Can Stop Us", the single that announced them in 1991, Sarah Cracknell seems a star again, soulfully singing this post-rave empowerment anthem straight to our hearts. Like the band, it has deepened with age.