Banksy auction prank leaves art world in shreds.

Banksy has released a video showing how he secretly built a shredder into one of his paintings that self-destructed after it was sold for more than £1m.

The framed Girl With Balloon, one of the artist's best known works, was the final item in an auction at Sotheby’s in London on Friday night and its sale price equalled the artist’s previous auction record of £1.04m.

Moments after the piece was sold, the canvas of a girl reaching for a heart-shaped balloon shredded itself.

Quoting Picasso on his Instagram, Banksy wrote: "The urge to destroy is also a creative urge - Picasso."

"It appears we just got Banksy-ed," said Alex Branczik, Sotheby's senior director and head of contemporary art in Europe.

Earlier, Banksy posted a picture of the moment it happened on his Instagram, with the words: "Going, going, gone..."

In 2017, Girl With Balloon, which originally appeared on a wall in Great Eastern Street, London, was voted the nation’s favorite artwork.  Girl with Balloon had enjoyed annual increases in value of about 20% in recent years.

Sotheby's has not revealed who bought the piece before it was shredded.

At the moment it is unclear whether their contract still stands.

Mr Branczik told the Financial Times the auction house was trying to "figure out" what the stunt means. He said: "We have not experienced this situation in the past ...where a painting spontaneously shredded, upon achieving a [near-]record for the artist.

"We are busily figuring out what this means in an auction context."  Sotheby’s said in a statement to the Financial Times: “We have talked with the successful purchaser who was surprised by the story. We are in discussion about next steps.” The auction house declined to reveal the identity of the buyer.