The satirical work was first known as "Question Time," after the weekly prime minister's questions in the British parliament, and renamed following minor alterations by the artist.
"Record price for a Banksy painting set at auction tonight," the artist wrote on Instagram as he posted a quote critical of expensive art. "Shame I didn't still own it."
The painting was exhibited in March at Bristol Museum, in the secretive Banksy's reported home city, to mark the date that Britain had been scheduled to leave the European Union.
"I made this 10 years ago. Bristol museum have just put it back on display to mark Brexit day," Banksy wrote on his Instagram account in March, adding the quotation: "Laugh now, but one day no one will be in charge."
Sotheby's noted that the work was offered at auction "exactly a year on from the unprecedented media storm surrounding the first ever creation of an artwork during a live sale."
It was referring to the auto-destruction of Banksy’s "Girl with Ballon," now known as "Love is in the Bin," as the gavel came down to seal the final bid of 1.04 million pounds at a Sotheby's auction in Ocotber 2018.
Sotheby's said Banksy, whose identity remains a mystery, had staged an "artist-driven hoax at the auction house’s expense that epitomizes [his] anarchic and rebellious spirit."
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