Its subject, Sue Tilley, has been interviewed extensively in the US and British media, telling how she was paid just 40 dollars to pose for the painter but immensely enjoyed the experience.

Tilley, nicknamed "Big Sue", joked she was the first nude pin-up to grace the front page of the Financial Times newspaper, which carried a photograph of the painting last month.

"I can't quite believe it, to be honest," she told the BBC.

Tilley, who now manages a job centre in London, said she was introduced to Freud by a friend and became his muse, often going for lunch with the artist before posing.

Freud, the 85-year-old grandson of pioneering psychoanalyst Sigmund Freud, was born in Berlin but his family fled Germany as the Nazis rose to power and he became a British citizen.

He has said: "I paint people, not because of what they are like, not exactly in spite of what they are like, but how they happen to be.

What do you think of the painting?