De Niro has been developing the musical for six years

"We're hoping it will run for about 20 years," he joked.

The futuristic �7.5m production, six years in the making, is one of the most expensive musicals ever staged in London.

Playing at the Dominion Theatre, it portrays a world where musical instruments have been banned, and boy bands and girl bands dominate.

But a group of rebels set out to find mythical electric guitars which were set in stone many years earlier.

The idea for the musical hit De Niro more than six years ago when he met Queen members Brian May and Roger Taylor at the Venice Film Festival.

The actor has said that the idea was something he was "interested in" and that he knew it would be a "great idea" for a musical.

Originally there were plans to base the musical on the story of the band Queen, but guitarist May has said that would have been "embarrassing" for the figures involved.

Queen were one of the biggest bands in the world in the late 1970s and 1980s but lost their main creative force and lead singer Freddie Mercury, when he died in 1991.

'Painful'

Taylor told the Evening Standard newspaper that he "couldn't bear the idea" of a musical based on the band's history.

He added: "It would be too painful, too close, and a bit grand. It would be for somebody else to do. You can't supervise your own history."

Elton also wrote The Beautiful Game

We Will Rock You weaves in lyrics and characters from some of the band's best-known hits - Bohemian Rhapsody, Radio Ga Ga and I Want To Break Free.

The story features a hero, Galileo, who is trying to find electric guitars because there is no rock music.

However he is being chased by the Ga Ga Cops who want to bring him to the Killer Queen.

Actor Nigel Planer, who has starred in The Young Ones and Comic Strip, is one of the show's stars.

Last week Queen's Bohemian Rhapsody was voted the UK's best single of all time in a poll of music fans.

The pop epic beat John Lennon's Imagine and Hey Jude by The Beatles in the survey by the Guinness Book of British Hit Singles.