Portrait of boy who calmed suicidal Freud set to sell for £4m

A painting by the late Lucian Freud that provides a fresh glimpse into his state of mind during one of the most turbulent periods in his life is expected to fetch £4m when it is sold at auction next month.

The 1952 work, Boy's Head, is one of the most recognisable of Freud's early paintings. It depicts Charlie Lumley, who lived near the artist in Paddington in London when he was a boy, and became one of the artist's most celebrated subjects.

Speaking ahead of the auction, Mr Lumley, now 79, described how he had to "babysit" Freud because Freud's friends, including the painter Francis Bacon, feared for his life. He said Freud was "fraught" because of his relationship with Lady Caroline Blackwood, Freud's wife at the time and another of his subjects.

"Francis [Bacon] said to me, for Christ's sake watch him because I'm afraid he's going to jump off the roof," said Mr Lumley. "So I had to babysit him for a while."

Several months before the painting was made, Freud, who died in July, had eloped to Paris with Lady Caroline, a member of the Guinness dynasty. Sotheby's says the canvas for Boy's Head was made in Paris, suggesting it was purchased by Freud during his flight from London. Lady Caroline was immortalised in Freud's 1952 works Girl in Bed and Girl Reading.

Soon after the artist's stay in Paris Freud returned to his Paddington flat, where he had forged a close relationship with Mr Lumley and his brother Billy.

Mr Lumley said he and Freud would visit nightclubs after periods of sitting at night. "You had to know you were in for a long sitting," he said. "No stops or breaks or things like that. Sometimes he'd do the background so you could relax, or if he was working on the hands you could shut your eyes."

Freud's marriage to Lady Caroline dissolved within several years. She moved to New York to study acting in 1957, and they were divorced.

Mr Lumley said Freud "never stopped talking". "He could converse on anything, you know," he said. "He had a marvellous memory. He could talk about boxing, which I used to talk about a lot, though how he knew about boxing, God only knows."

Michael Macaulay, deputy director of specialist contemporary art at Sotheby's, said buyers' interest in Freud's work had increased since the painter's death. "It's a very recent event and that's usually what happens," he said. "The estimate for this work is extremely realistic, and we are feeling confident."

In 2005 Freud said of this period: "I felt that the only way I could work properly was using absolute maximum observation ... I had a lot of eye trouble."