The Sonisphere festival will not go ahead this year, organisers have announced. The event – due to take place at Knebworth in the summer – has been cancelled for 2015 after bosses admitted they'd been unable to sign a bill they believed was "good enough."

The shock announcement came at 6pm today via the festival's official website, Facebook and Twitter accounts.

It reads: "Team Sonisphere reluctantly confirm that Sonisphere will not take place in the UK in 2015. We’ve been working hard to get a lineup that we felt was good enough, but also on a weekend which would avoid other events that we know rock fans would want to support.

"Unfortunately our last irons in the fire have just been extinguished and it’s clear that we won’t be in a position to run the event this year. We’ve said in the past that Sonisphere will only go ahead if we feel it is going to be good enough and that hasn’t changed.

"We hope all rock fans have a great summer with all the festivals and concerts already in the calendar and we plan to see you all in 2016."

Last year's event was headlined by METALLICA, IRON MAIDEN and THE PRODIGY.