Onlookers at a Sotheby‘s auction earlier this month were left gobsmacked when, just moments after selling to a European collector for more than £1m, , with the bottom half reduced to strips dangling from the bottom of the frame.

In a new video, entitled Shred The Love, The Director‘s Cut, Banksy has revealed that he carried out rehearsals for the headline-grabbing prank, and that in practice runs the secret shredder hidden inside the painting‘s Victorian-style frame had “worked every time”.

0:22 Video: Banksy's shredded art did not go to plan

Footage of a test run shows a Girl With Balloon print passing through the shredder in full, with none of the canvas remaining intact.

Posting on Instagram, the anonymous artist said: “Some people think it didn‘t really shred. It did. Some people think the auction house were in on it, they weren‘t.”

The new three-minute-long video – the second to be released by the artist giving details on the stunt – shows a hooded figure constructing the shredder in a workshop.

Image: The video shows the shredder being inserted… Image: … and the shock when people realised what had happened at the auction

It then cuts to the now world-famous auction, where a pair of hands presses a button in a black box to set off the destruction as soon as the hammer goes down.

The new half-shredded artwork has been renamed Love Is In The Bin after being granted certification by Pest Control, Banksy‘s authentication body.

Sotheby‘s has confirmed that the buyer, a long-standing female client, still wants to take the work for the agreed price.

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

The artwork was signed and dedicated and the vendor acquired it from the artist in 2006, the auction house said.

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The lot had been estimated to sell for £200,000 to £300,000 before the auction.

Some experts believe the prank has increased the value of the artwork.

Love Is In The Bin is the latest in a long history of anti-establishment statements by the street artist, who rose to prominence through a series of graffiti pieces across the country.

Other recent works included the opening of Dismaland, his dystopian, Disneyland-esque theme park in 2015, which he described as a “family theme park unsuitable for children”.