Sotheby's will offer two masterpieces by British artist Francis Bacon, including the triptych Three Studies of Isabel Rawsthorne, as part of its Contemporary Art Evening Auction.

Rawsthorne also served as a muse for Picasso, Giacometti and Derain

The three works of Isabel Rawsthorne, Bacon's close friend and fellow artist, will sell with a £10m-15m ($15.3m-23m) estimate on June 26 in London.

Head III, which featured in Bacon's first solo show in 1949, the Hanover Gallery exhibition, is expected to bring £5m-7m ($7.6m-10.7m).

The pairing of the two paintings at Sotheby's is fitting, as it was in preparation for the Hanover Gallery exhibition that Bacon met Rawsthorne, who was herself preparing for a solo show at the gallery.

Rawsthorne soon became a huge source of inspiration for Bacon. She had already served as a muse to artists such as Andre Derain, Pablo Picasso and Alberto Giacometti.

Their relationship developed until Rawsthorne became one of Bacon's closest friends - as well as one-time lover - and the artist often portrays her in a somewhat heroic light, obviously enamoured with her glittering past as a darling of the Parisian avant-garde in the 1930s.

The present work was executed in 1966.

Head III is an important work in the development of Bacon's technique, acting as a precursor to the lauded Screaming Pope series

Head III is a superb transitional piece that demonstrates the progression of a crucial series in Bacon's oeuvre. This was the first time that Bacon had truly portrayed the carnal ferocity that he has now become known for, as well as serving as a precursor to his landmark Screaming Pope series.

In November 2012, one of the finest works in Bacon's Screaming Pope series sold for $29.7m at Sotheby's New York, making a 19% increase on its high estimate.