An oil masterpiece by Irish painter Francis Bacon fetched almost £18 million at a London sale while a portrait of Chairman Mao by Andy Warhol netted £7 million.

Bacon’s moody 1953 work Study for a Portrait was snapped up by an anonymous bidder at Christie’s Post-War and Contemporary Art auction, which realised £78,817,050 in total.

The two metre by 1.4 metre piece, described by the auction house as “an arresting and dark study in the degradation of power”, eventually sold for £17,961,250, almost £7 million more than the pre-sale estimate.

It is the second highest price paid for a work at a Christie’s post-war and contemporary art auction after Bacon’s Triptych, which sold for £26.3 million in 2008.

Iconic pop artist Andy Warhol’s 1973 acrylic of former Chinese leader Mao Zedong fetched £6,985,250 while Woman Smiling, a 1958-59 portrait by Lucian Freud, sold for £4,745,250.

Five artist records were set at Tuesday’s sale for Juan Munoz, Ron Mueck, Paula Rego, Domenico Gnoli and Miquel Barcelo, who broke the record for any living Spanish artist.

“We are extremely pleased to have established a world record price for a work of art by a living Spanish artist with Barcelo’s sublime bullfight painting,” said Francis Outred, the head of post-war and contemporary art at Christie’s Europe.