Rockers U2 turned back time as they took to a roof-top in London last night for a surprise gig to mark the launch of their new album.

Some 5,000 onlookers gathered below the BBC Broadcasting House building after rumours spread on the internet that the band would be staging an impromptu performance.

Police were forced to close a number of streets and divert traffic as fans poured in to catch a glimpse of the high-rise show.

The band belted out a number of songs from the new album, including 'Get on Your Boots' and 'Magnificent', as well as playing previous material such as 'Beautiful Day' and 'Vertigo'.

The scene was reminiscent of the occasion, more than 20 years ago, when the band took to the rooftop of a Los Angeles liquor store to serenade delighted fans with 'Where the Streets Have No Name'. Although, unlike last night, that gig ended up being shut down by irate police.

And while the group are well used to rocking out stadiums, they will be changing tack with a series of "intimate" outdoor concerts this summer.

Speaking on BBC Radio 1 yesterday, a vague Bono said they had "something very special planned".

The frontman explained it was "a whole way of trying to do shows outdoors and make them very intimate".

And, in a nod to the current financial climate, the singer said the band would be "trying" to provide some cheaper ticket prices.

However U2 will still be happy to charge higher amounts for those well-heeled fans who like to flash their cash.

"We're also going to have some very expensive ticket prices because rich people have feelings too," joked Bono.