The composer Andrew Lloyd Webber is selling an early portrait by Pablo Picasso of a bohemian friend to raise money for his charitable foundation. It is expected to make up to £33m.
The painting of Angel Fernandez de Soto, dating from Picasso's Blue Period early in the 20th century, is currently on show in the National Gallery's Rebels and Martyrs exhibition but will be then sold by Christie's in New York in the autumn.
Guy Bennett, the auctioneer's senior vice-president, said Christie's was "thrilled" to be selling a work of such stature. "The dramatic and intense friendship of the artist and his subject makes this one of the most personal and powerful works from the Blue Period," he said.
Picasso met Angel de Soto in 1899 at the Els Quatre Gats café, an artists' gathering place, in Barcelona, the city to which his family moved from Malaga when he was a teenager.
The young artist quickly became friends with the penniless dandy De Soto. They briefly shared a studio until De Soto's penchant for women and entertaining made that arrangement impractical. Yet they remained friends until De Soto was killed in the Spanish Civil War in 1938.
This painting was produced in 1903, the year before Picasso left his homeland to settle in Paris.
The work, which is one of the rare masterpieces of non Pre-Raphaelite art in Lloyd Webber's collection, will be sold on 8 November, but he will receive nothing personally from the sale. It is the Andrew Lloyd Webber Art Foundation which will benefit.
"If the picture sells successfully, it will be fantastic to have a charitable fighting fund with the freedom to support other excellent causes, particularly in the theatre and music worlds," he said.
Among those causes are the training and education of young performers, although no decision will be made on how the money will be spent until the results of the sale are known.
Sir Nicholas Lloyd, a spokesman for the foundation, said: "The market for a painting such as this is currently so strong the trustees of the foundation believe that to have such a huge amount of money locked up in one painting which could be used for other causes is hard to justify."