A Banksy painting has "self-destructed" just moments after selling for more than £1m.

Girl With Red Balloon was one of the star attractions at Sotheby's Contemporary Art Evening Sale in London.

Depicting a girl reaching towards a bright red heart-shaped balloon, the spray paint and acrylic on canvas is one of Banksy's best-known images.

The auction house said the painting was signed and dedicated and that the vendor had acquired it from the artist in 2006.

The winning bid of £860,000 (£1,042,000 including buyer's premium) was given by phone at around 9 p.m., well over the pre-auction estimate of between £200-300,000.

But just after the hammer went down, the painting was shredded, thought to be by a remotely activated mechanism within the frame.

The prized work then came out of the bottom in strips.

If a work is damaged while in the care of an auction house, a buyer would not normally be expected to go through with the purchase.

But perhaps, now known as the subject of one of the greatest pranks in the art world, Girl With Red Balloon will be worth even more in its shredded state.