Chris Martin joins REM on stage

REM mixed old hits and new songs during their unannounced set.

Coldplay singer Chris Martin joined US band REM on stage at the climax of Oxfam's Make Trade Fair benefit show in Hammersmith, London, on Tuesday.

The British star joined REM's Michael Stipe on vocals for Man on the Moon during their "surprise" headline set.

The event also featured Jamelia, The Thrills, actress-turned-singer Minnie Driver and comedian Ricky Gervais.

Coldplay have been big supporters of Make Trade Fair, which calls for reform of world trade laws to reduce poverty.

"I was introduced to the idea of fair trade because I'm a massive Coldplay fan, so I'd like to thank Chris Martin," Stipe told the crowd.

Speaking at a press conference before the event, Driver said fair trade was "not the sexiest of campaigns".

Oscar-nominated actress Minnie Driver is launching a singing career

But the Oscar-nominated actress - whose debut album is released in October - said musicians had "a great platform to educate and encourage kids to take an interest in what's going on globally".

"I don't think kids know poverty is the most preventable cause of death in the world, and trades will go a long way to alleviate it," she said.
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