A museum in Banksy's home city has been caught selling a hugely popular print of one his artworks without permission.
Bristol Museum and Art Gallery - which was once "taken over" by the elusive street artist - had been doing a roaring trade in its £5 prints of the Angel Bust, selling a copy every minute at one point.
But a buyer contacted Banksy's agent on Monday to find they were unauthorised.
The museum has since apologised and withdrawn the prints from sale.
Steve Hall, a Banksy fan from Asheville, North Carolina, USA, was disappointed to learn his purchase was unauthorised and cancelled his order.
He said: "I sent an email to Banksy's website to find out if the Angel Bust print sold by Bristol Museum was authorised by Banksy.
"This was their response: 'Absolutely not, they were printed without our permission.'"
Banksy, an anonymous street artist from Bristol, created the angel sculpture with a tin of pink paint tipped over it for a takeover of the museum in 2009.
Hundreds of thousands of people queued to see Banksy versus Bristol Museum after the artist transformed it into a menagerie of "unnatural history".
He left the statue when the exhibition closed.
The print was available for some time but sales surged after it went on sale in the US and Japan - with as many as 1,000 sold in a single day.
A spokesman for Bristol City Council, which runs the museum, said: "We own the artwork in question and had been granted permission to produce the image in our guide to the art gallery published last autumn.
"It was assumed that this would allow us to produce prints, however, having contacted Banksy's management we were told that this was not the case.
"As a result we have taken the decision to withdraw all prints from sale and offered full refunds to any customers.
"We have apologised to Banksy and would like to offer our apologies to any customers who felt misled by this sale."