A pair of paintings by Tony O'Malley, featuring an unfinished nude by Francis Bacon on the reverse, sold at Christie's on March 17.
O'Malley lived and worked in St Ives, UK during the 1950s along with Bacon, who rented the adjacent studio in 1959.
After a blazing row with his partner Ronnie Belton in January 1960, Bacon left suddenly for London - leaving behind all his equipment and a series of half-finished canvases.
These were dished out by the owner of the studio to various local artists to make use of.
O'Malley was given this half-finished nude on a board. Another painting, given to sculptor Bill Featherstone, was used as a roof for a chicken shed.
A possibly apocryphal story states O'Malley was approached by a dealer from London, who offered him a large sum of money to complete the painting in Bacon's style.
This enraged O'Malley, who split the board in two.
Contemporaries of the artist, however, have said that he simply preferred painting on a smaller scale.
Whatever the truth, it was undoubtedly the biggest hit of the sale - achieving £434,500 ($629,490) against an estimate of £30,000 ($43,463).
That's an increase of 1,348%.
The value of Bacon's work has increased dramatically in recent years, with his Three Studies for a Portrait of Lucian Freud selling for the then world record price of $142.4m in 2013.
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