Coldplay singer Chris Martin helped convince Beyonce Knowles to appear at Glastonbury.

The 'Run the World (Girls)' singer was apprehensive about signing up for the festival - one of the Europe's biggest - after her husband, Jay-Z's, inclusion on the 2008 bill proved controversial, but Chris helped talk her round, according to co-organiser Emily Eavis.

She told Radio Times magazine: "Chris is a bit wary of people knowing he's been so involved. I don't know why because it's actually cool.

"Chris is as loyal as they come - he'll do anything for Glastonbury. He's really an unlikely frontman. Most people are a bit more all-consumed with their own thing."

Emily invited Jay-Z to perform at the festival, and although his set was hailed a success, Oasis guitarist Noel Gallagher had complained hip hop at the festival was "wrong", prompting a media storm.

Emily said while Beyonce - who releases her new album '4' next week - has been keen to play since she saw Jay perform, they had to book her as early as possible.

Emily added: "Luckily, we spoke to Beyonce before she planned her tour this year, so she managed to put Glastonbury in her schedule, then build a European tour around it."

Glastonbury Festival starts on Wednesday (22.06.11) and sees headline sets from Coldplay, U2 and Beyonce.