A portrait of a young woman, which had been dismissed as a fake Raphael and lay forgotten in the basement of an Italian palace for 40 years, has been confirmed as genuine by art experts and could be worth up to £25 million.

The newly-discovered 12 by 16 inch oil painting was long thought to have been a copy made in the style of the Renaissance master long after his death and dismissed as almost worthless.

But art historians now believe it to be a first draft by Raphael of part of a larger painting, The Holy Family (or 'The Pearl'), which hangs in Madrid's Prado museum.