Francis Bacon’s Three Studies for a Portrait of George Dyer (1963) will sell at Christie’s.

The work, which originally belonged to acclaimed author Roald Dahl, is expected to make around $50m-70m in an auction of post-war and contemporary art in New York on May 17.

Author Roald Dahl bought the triptych from Francis Bacon circa 1964-1967

Prior to then it will be on display at Christie’s London between February 24 and March 8.

This is the first time it has ever appeared at auction.

Dahl acquired it (along with three other Bacon works) directly from the artist between 1964 and 1967.

It's Bacon's first portrait of George Dyer, the love of the artist's life. The two men had an intense and violent relationship that ended with Dyer’s suicide in 1971.

Demand for Bacon’s work has been growing since the 1990s, culminating in the sale of his Three Studies for a Portrait of Lucian Freud for a record $142.4m in 2013.

Loic Gouzer, deputy chairman of post-war and contemporary art, says: “Three Studies for a Portrait of George Dyer is a masterful tryptych, which was completed within the first three months of Bacon’s relationship with the most important muse of his career.

“These powerful portraits exemplify the dynamism and complex psychology that the artist is most revered for.

“And with its tremendous significance to the artist and excellent provenance, we are honored to have the opportunity to present this monumental work at auction for the first time.”

We’ve got a remarkable range of art and photography memorabilia for sale.

Please sign up to our free newsletter to receive exciting news about art and photography auctions.