MORE additions to the 2011 Sonisphere Festival line-up for Knebworth House this summer are due to be revealed.

The three-day rock event returns to grounds of the Hertfordshire stately home from Friday, July 8 to Sunday, July 10.

Although main stage headliners Metallica, Biffy Clyro and Slipknot have been known since before Christmas, organisers are expected to reveal more acts playing the UK leg of the international touring festival in the coming week.

Comedian Bill Bailey was confirmed as the Saturn stage headliner for the Sunday night in the last announcement, with the former Never Mind the Buzzcocks team captain taking the stage directly before American metallers Slipknot.

A statement released at the time said: “With more stages still to be announced, including more comedy, fantastic bands and other alternative performances, Sonisphere Knebworth 2011 is going to be simply unmissable, and with weekend tickets selling at an ever more rapid pace, is heading towards its first full sell out.”

Heavy metal band Cavelara Conspiracy have self-confirmed on their website they are playing Knebworth this summer.

American bluegrass rockers Hayseed Dixie have also said on their website they are on the Sonisphere bill.

Tickets for Sonisphere UK are available from the festival’s official website at www.sonispherefestivals.com

With weekend camping tickets selling faster than last year, there’s no guarantee day tickets will go on sale.

* Legendary guitarist Slash, ex of Guns N’ Roses, has been confirmed for Sonisphere Spain a week after Knebworth on July 15-16.