A portrait of Francis Bacon's former lover George Dyer has sold for £42.2m, smashing its pre-sale estimate of £28m.
Christie's said the 6ft-tall artwork, entitled Portrait of George Dyer Talking, was the most valuable work of art it had sold in Europe.
It was bought by an anonymous telephone bidder at Christie's Post War and Contemporary Art auction in London.
Dyer died of an overdose in Paris two days before the painting was exhibited at a Bacon retrospective in 1971.
Dyer and Bacon had become involved after Bacon caught Dyer burgling his house.
The canvas depicts the artist's lover perched on a stool, his twisted body positioned under a naked light bulb.
The 1966 painting is understood to have been sold by Mexican banker David Martinez Guzman. It last appeared on the open market in 2000, when it sold for £4m at Christie's in New York.
The most expensive Bacon work ever sold at auction was his triptych of Lucian Freud, which sold for £85.3m ($142m) last November.
Also in the sale was Abstraktes Bild, a large abstract canvas by Gerhard Richter from 1989, which fetched £19.5m.
Jeff Koons' Cracked Egg (Magenta) fetched £14m - with the seller reported to be Koons's friend and colleague Damien Hirst.
Hirst's own Mickey Mouse depiction fetched £902,500, with all the proceeds going to children's charity Kids Company.
The work, which represents the figure of the Disney character with a series of large circles, went for three times more than the expected price.
Speaking after the auction, the charity's founder, Camilla Batmanghelidjh, said: "Some childlike magic happened tonight... in reality, Mickey came to the rescue of some of the most vulnerable children.
"This money will change lives. From the bottom of my heart, thank you, Damien."