(Bloomberg News) A Francis Bacon self-portrait sold tonight in London for 4.5 million pounds ($7 million), including fees, at the beginning of a week of auctions that will test international demand for contemporary art.

The 1980 canvas "Study for Self-Portrait" was estimated at 5 million pounds to 7 million pounds at hammer price in Sotheby's 79-lot sale of contemporary artworks. One of six works in the auction that was guaranteed to sell, thanks to a third- party "irrevocable bid," the painting attracted one bid from Cheyenne Westphal, Sotheby's European head of contemporary art.

The Bacon had been purchased by its seller for $1.8 million at Sotheby's sale of the collection of Stanley J. Seeger in New York in May 2001. An earlier single-panel portrait, dating from 1969, sold for $33.1 million at Sotheby's, New York, at the height of the last art-market boom in November 2007.

This week's auctions of works by established and emerging artists at Sotheby's, Christie's International and Phillips de Pury & Co. are estimated to raise as much as 290 million pounds. The sales follow the Art Basel fair in Switzerland earlier this month and Sotheby's 41.4 million-pound auction of the Gunter Sachs collection in London on May 22-23.

Basquiat's 'Warrior'

The top price was the 5.6 million pounds given for Jean- Michel Basquiat's 1982 painting "Warrior," showing a lone black figure brandishing a sword.

Another of the evening's guaranteed highlights, this had been acquired by its seller at Sotheby's, London, in 2007, for 2.8 million pounds. Five years on, it was revalued at 5 million pounds to 7 million pounds. Competition was muted, the winning telephone bid adding just 50,000 pounds to the pre-agreed price.

Glenn Brown's monumental landscape "The Tragic Conversion of Salvador Dali (After John Martin)" sold for a record 5.2 million pounds to a telephone bid taken by Oliver Barker, Sotheby's senior international specialist. He beat five other telephone bidders.

Also guaranteed by an "irrevocable bid," this 1998 work by the keenly-collected U.K. artist, combining science fiction elements with apocalyptic Victorian landscape, had been estimated at 2.2 million pounds to 2.8 million pounds. It had been included in the recent exhibition of works by the 19th- century painter John Martin at Tate Britain, which identified the owner as the London-based private dealer Ivor Braka. Braka, seated in the room, smiled at the result.

Brown's 'Filth'

The previous highest price for Brown was the $2.5 million paid for the 2004 panel painting "Filth" at Phillips de Pury in New York in May 2011.

Increasing numbers of affluent individuals are looking to buy investment-grade art, particularly by fashionable contemporary names, to provide prestige decoration for "super- prime" homes and to store value at a time of economic and financial-market volatility.

A 2011 Deloitte survey of 19 private banks, mostly in Luxembourg, reported that 83 percent of respondents said there were strong arguments for including art in wealth management.

The average price of successful lots at the New York evening contemporary-art auctions in May was a record $5 million with fees. Gerhard Richter and Andy Warhol were among just eight artists that accounted 69 percent of the value at those sales, said the London-based analyst company ArtTactic.

Sotheby's auction is estimated to raise between 57.5 million pounds and 82.5 million pounds.