E.O.W. on her Blue Eiderdown V, a stunning work by the leading British artist Frank Auerbach, doubled its pre-sale estimate at Bonhams' Post-War and Contemporary Art sale in London on 11 February, achieving the highest price ever for a painting of a figure by the artist.

Other highlights included Untitled (Red Fan), the first sculpture by Gutai co-founder Kazuo Shiraga ever to come to the auction market, which sold for £1,538,500, the highest price achieved for any Gutai sculpture. Peju's Robe, by El Anatsui, also smashed its pre-sale estimate of £450,000-550,000 to sell for £806,500.

E.O.W. on her Blue Eiderdown V had not been seen in public for half a century. It is a painting of Estella West, Auerbach's most inspirational model.

Auerbach met West, a widowed mother of three in her thirties, when he was just a teenager – he moved into her basement as a lodger and they became lovers. For years, Auerbach painted her obsessively, but E.O.W. on her Blue Eiderdown V, with its wonderfully thick impasto and glorious colours, is the largest and undoubtedly the most impressive of his E. O. W. series.

A second work by Auerbach, The Studios II, sold for £422,500 - well over its pre-sale estimate of £280,000-380,000.

The packed saleroom also saw fiercely competitive bidding for Banksy's Keep it Real, which sold for £194,500 against an estimate of £100,000-150,000, and Victor Vasarely's TALLER-VV, which nearly tripled its estimate of £50,000-70,000 to sell for £146,500.

A strong section of Post-War Italian art, featuring works by artists including Alighiero Boetti and Lucio Fontana, also performed well. It was led by Guilio Paolini's Vis-à-vis (Alessandro), an important work from 1992, which achieved £92,500 – four times its low estimate. Three ceramic works by Fontana confirmed the upward trend for this artist's work.

"The carefully curated selection of lots in the sale explored value in all of its definitions across the world. The competitive bidding and high prices achieved today are testament to the sensational nature of the works offered," said Ralph Taylor, Bonhams Senior Director of Post-War and Contemporary Art. "It has been a particular honour to sell the first Shiraga sculpture offered at auction and to set the new standard for this artist, whose global significance is ever-growing."

The sale itself well-exceeded its estimate of £4,500,000, achieving a total of £6,361,525.