Justin Makes Surprise N.E.R.D. Appearance

Pop star Justin Timberlake caused mayhem when he made an unannounced appearance with pals N.E.R.D. at their Brixton Academy gig in London on Sunday night.

The Rock Your Body singer came onstage after friend Pharrell Williams' band had performed just three tracks - and then stayed for almost the entire set.

Crowd hysteria reached fever pitch when Justin - who's been in Britain since the MTV EMAs - sat down at the keyboard for a rendition of Senorita.

A crowd member says, "The place went wild when he came on stage. Girls were trying to get up on the stage to dance with him during the performance."

He then contributed to the choruses of N.E.R.D. songs Rock Star and Bobby James, as well as closing the encore with a "riotous" Lapdance.