It languished for centuries at Castle Howard in Yorkshire

It is said to date from between 1494 and 1504 and is regarded as a major work.

The drawing may have been bought by Henry Howard, the 4th Earl of Carlisle in 1747 from the well-known English collector Jonathan Richardson Senior.

It may now be offered to the National Gallery of Scotland in Edinburgh, but if the gallery cannot raise the asking price, it could then be sold at auction where it is expected to reach between �6m - �8m.

Simon Howard, who owns the stately home, said: "Clearly this is a drawing of major importance which has been accepted by all the experts as being by Michelangelo and as such it should be on display in a national gallery or museum where everyone can enjoy it."

Like finding part of the Holy Grail

James Miller, Sotheby's

Castle Howard has already handed over three other paintings from its private collection to the National Gallery of Scotland.

If the gallery is not interested, it is likely that Woman Draped Mourning it might go to the Walker Art Gallery, in Liverpool, if they can raise the funds.

There are only three extant Michelangelo drawings in private collections. In July a Michelangelo drawing of the Risen Christ was sold at Christie's for a record �8.14 million.

Shock discovery

Woman Draped Mourning's identity was only rediscovered when Sotheby's specialist Julien Stock took a close look at the scrapbook. "What I thought when I first saw the drawing is unprintable," he told London's Evening Standard newspaper.

"I realised this was a major drawing by Michelangelo. No one had any idea it was here."

Art experts are estatic at the discovery which James Miller, deputy chairman of Sotheby's, described as "like finding part of the Holy Grail".

He added: "It is the most significant Michelangelo work to be discovered in living memory. It is of colossal importance - this is a major drawing."