The donor flew to Australia from the US last year to personally hand over the painting, "Jeune fille endormie", which is one of the largest gifts ever made to the University of Sydney.

The vivid painting, which measures 18 inches tall by 22 inches wide, was painted in 1935 and depicts Picasso's lover and muse, Marie-Therese Walter. It has only been shown once in public before now.

In June, the artwork, which shows Walter asleep with her head leaning on her crossed arms, will be sold at Christie's auction house in London and is expected to fetch between £9 million and £12 million. Last year, a 1932 portrait of Walter by Picasso, "Nu au Plateau de Sculpteur" set a world record when it was snapped up by a mystery bidder for $106.5 million (£65m).

Michael Spence, Sydney University vice-chancellor, said the "extraordinary act of generosity" came with three conditions.