Queen rocker Brian May is adamant late legend Freddie Mercury would give singer Adam Lambert the "seal of approval" as the flamboyant star prepares to front the band at an upcoming festival.

The former American Idol contestant will perform in Mercury's place when Queen headline the Sonisphere festival in Knebworth over the summer.

And guitarist May insists the band's iconic star, who passed away in 1991, would be happy with their latest addition.

He says: "Judging by my incoming mail, this decision will make a lot of people very happy. It's a worthy challenge for us, and I'm sure Adam would meet with Freddie's approval! And what better place to revisit, and walk those emotional paths than Knebworth? It will be a rush."

And Lambert admits he can't wait to get on stage with his heroes, adding: "I'm completely in awe of the Queen phenomenon. The thought of sharing the stage for a full set is so beautifully surreal. I'm honoured to be able to pay my respects to Freddie's memory. He's a personal hero of mine and I am deeply grateful for the chance to sing such powerful music for fans of this legendary band. I know the evening will be a huge milestone for me, and with the support of Brian, Roger (Taylor, drummer) and the rest of the band I know magic will be on display."

Lambert previously performed with the surviving members of Queen at the MTV European Music Awards in November.