Organisers of the UK festival Sonisphere have announced plans for an event celebrating 40 years of festivals at Knebworth.

Visitors to Sonisphere's website are now greeted by a poster for the event, which can be seen above. The advertisement trails what appears to be a three-day event running between July 4-6 at Knebworth Park in celebration of the past four decades of festivals on the site.

Sonisphere took a "year off" in 2013. The hard rock festival, which began in 2009 and took place at Knebworth, was cancelled in 2012, casting doubt over whether it will ever return.

The 2012 Sonisphere festival was due to feature performances from Kiss, Queen and Adam Lambert and Faith No More More. On announcing the cancellation, organisers said that co-ordinating the festival to an appropriate standard that year had proved more difficult than expected.

Artists who have performed at Knebworth over the past 40 years include Oasis, Led Zeppelin, Queen and Robbie Williams.