Biffy Clyro are set to headline next year’s Sonisphere festival in Knebworth, it’s been announced.

The band will join previously announced headliners Slipknot at the event, which will take place earlier than normal from July 8-10, 2011.

Slipknot's appearance, part of a European tour, will mark one of the band’s first performances following the death of founding member Paul Gray earlier this year.

“This tour is about us and our fans,” Slipknot said in a statement.

“It’s about celebrating the life of our brother, Paul and his legacy. The door is neither open nor closed. This tour is about burning down that door.”

Further headline announcements are due to be announced shortly.

(by Jason Gregory)