The Flaming Lips, Apollo Hammersmith, London

The man in the white suit is The Flaming Lips' ringleader and mastermind, the P T Barnum of rock'n'roll. For 20 minutes before tonight's performance begins, Wayne Coyne is on stage with the road crew, ensuring all the elements are in place for the Lips' spectacular stage production to reach optimum impact. The show is another milestone in the Lips' journey from underground curios to psychedelic aristocrats. Discounting festival appearances, it is, Coyne proudly tells us more than once, the biggest gig the Lips have played since they emerged from Oklahoma City in 1984.

Almost two years since its release, their latest and greatest album, Yoshimi Battles the Pink Robots, still has promotional legs. And as his wide-eyed declarations of love and loyalty to the audience make clear, Coyne is eternally grateful for the opportunity to unfurl his sound and vision one more time. The group have wooed the mainstream with performances hinged on simple but lavish spectacle. A host of celebrity fans including Justin Timberlake, who guested on a Top of the Pops performance, dressed in a dolphin suit, have lined up to sing their praises.

The Lips pay tribute to another fan early in the set when Coyne hollers The White Stripes' "Seven Nation Army" through a loudspeaker. But it is their own songs that hold the crowd spellbound: delivered in Coyne's frail but compassionate voice, they blend ferocious drive and tender insight with baleful sorrow and outlandish celebration.

The presentation is Grateful Dead meets Disney or the stadium-rock performance art of Zooropa-era U2 given a punk-rock makeover. A large video-screen backdrop shows close-ups from the stage and the crowd, film of a topless go-go dancer in Wellington boots, an atom-bomb test, marching armies, Vietnam-era assassinations and several clips of the young Leonard Bernstein in full conducting flight. The last are masterfully sync-ed to the points when songs such as "Race for the Prize" soar into symphonic overload.

Three large mirror balls mounted on cement-mixers bathe the hall in refracted silver light. Balloons of various sizes bounce around the venue. Dressed as a pink elephant, Coyne's long-time accomplice and presiding musical powerhouse, Steven Drozd, plays keyboards while, on either side of the stage, various friends, journalists and competition-winners dressed in furry animal suits dance and frolic.

It is daft, baffling but uplifting theatre. The lion dances with the panda, and Coyne showers the audience with confetti glitter and brandishes a portable dry-ice generator during "Fight Test". As the show progresses, Coyne douses his head with increasing amounts of fake blood, and a gory anti-drug film-clip comes with the message: "Don't Snort Your Own Brain".

But the psychedelic freakshow is cunning subterfuge. At heart, Lips songs - such as the metaphoric "Yoshimi Battles the Pink Robots" or the gilded ballad "Waiting for Superman" - are deeply moral, hinged on honest virtues, personal resolve and determination. There is even something of Brian Wilson's utopian vision, albeit hardened by experience, in the beautiful "Do You Realise?".

Seen for a third or fourth time, The Flaming Lips' spectacular loses a little of its capacity to surprise, and Coyne's overearnest and overlong between-song raps can seem superfluous. But such carping misses the point - visually and musically, the Lips go places others fail to reach. If, after 20 years' toiling in the underground, their influence now spreads to a new generation, it can only be a good thing.