The one-off show at London's Royal Festival Hall was a curtain raiser for the band's forthcoming fourth album and a UK tour in September.

During their two-hour set, Radiohead played 21 tracks, including some of their complex, carefully-structured rock hits such as "Paranoid Android" and "No Surprises".

They also showcased their new songs - soaring new epics packed with dense heavy guitars.

Downbeat themes

The band are known for their downbeat themes of paranoia and alienation and the subject matter of their new material seemed to be along similar lines.

One song, "The Morning Bell", was about amnesia, while another was about people eating their dead.

Another song, "Optimistic", was reminiscent of Led Zeppelin's mystical outings, featuring singer Thom Yorke's fluid, gymnastic vocal.

Radiohead's performance was part of the annual Meltdown Festival at London's South Bank.

The venue is more usually used for sedate classical events, rather than rock acts like Radiohead.

The band agreed to play after the event's curator, maverick singer Scott Walker, approached them.

Radiohead have been out of the limelight for the past two years, concentrating on their fourth album.

Their most recent album, OK Computer, is widely regarded as one of the best records of all time, coming second to The Beatles' Revolver in a Q magazine poll of music writers conducted earlier this year.