There is absolutely no doubt about what stole the thunder this evening at Sotheby’s Frieze week contemporary art auction—and it was a bunch of monkeys.

Devolved Parliament, the massive painting by Banksy of chimpanzees sitting, chewing, scratching, and just generally being chimpanzees in Britain’s House of Commons sold for a record £9.9 million ($12.1 million). That total was nearly five times the high estimate of £2 million ($2.47 million). It was also by far a record for a work by the street artist at auction, which was previously the $1.87 million paid for Keep It Spotless at Sotheby’s New York way back in 2008.

Laughter, seemingly representing both delight and disbelief, spread throughout the room during the nearly 13-minute bidding battle.

Among the early bidders were Warhol/Basquiat/Hirst trader-collector Jose Mugrabi and Turkish banker Halit Cingillioglu, who first took the price beyond the low £1.5 million estimate. But they were soon submerged beneath a torrent of telephone bids—and one persistent bidder at the back of the room—until the Banksy fell to the phone manned by Emma Baker, Sotheby’s head of sale.

The painting was the top lot of the sale, coming equal with Pyro by Jean-Michel Basquiat, which performed less remarkably, selling within estimate. “It’s a big moment,” said Sotheby’s Alex Branczik after the sale, “when Banksy shares top price with Basquiat.”

Francis Bacon, Figure with Monkey (1951). Courtesy of Sotheby’s.

He might have added that it is a big moment when a Banksy painting of chimpanzees sold for more than a Francis Bacon of chimpanzees. Bacon’s 1951 painting, Figure with Monkey, sold just above its estimate for £2.8 million ($3.4 million) this evening to British art advisor Wentworth Beaumont.

It had been suggested that Banksy himself was the seller of the painting because the work had changed—it was darker in tone, with a few bananas added—since it was last exhibited. But Sotheby’s claimed that Banksy had simply asked the owner if he could make the changes. (This side plot amounted to a slightly less intriguing mystery than the one inspired by Banksy’s trick artwork Girl with Balloon, which self-destructed in the auction room last year after being sold, gaining worldwide press attention.)

The artist himself addressed the rumors on Instagram after the sale, posting an image featuring a quote from the late art critic Robert Hughes decrying high auction prices, and offering the laconic caption: “Record price for a Banksy painting set at auction tonight. Shame I didn’t still own it.”

So the seller remains a mystery.

“We gave it a shot but didn’t get it,” said Jonathan Cheung of the Maddox Gallery of Devolved Parliament. “It’s a super piece… No surprises at £10 million in my opinion—especially given the prices being achieved at the print level!”

Not all of the art world was so complimentary, though.

“I call BS to compare (favorably) his art to the art of Jean Michel Basquiat as ‘street artists,'” art advisor Josh Baer wrote in his auction newsletter, the Baerfaxt, after the sale. “Look at a JMB painting vs this work, which is pretty much a poster. If your art advisor is 14 years old, and has been pushing you to also go long Kaws, then the rest of us art advisors over 30 or whatever should just quit.”