A LOST masterpiece by Michelangelo which was sold at auction after being discovered in North Yorkshire has become the subject of an export wrangle.

The work, called Study of a Mourning Woman, was discovered pasted into an album of drawings in the library of Castle Howard, near York.

Experts say it had lain undiscovered in the pages of the book for 250 years.

It was later sold at auction for nearly £6m, heightening fears that it may one day be exported.

Worries that the rare drawing may be lost to the nation prompted the Government to place an export ban on it yesterday.

The temporary bar allows people two-months to put in offers to buy the work to keep it in the UK, but if no one comes forward the picture could still be lost.

Michelangelo's study was found among otherwise undistinguished artworks but is seen as a rare example of his earlier work.

It is one of only a handful of drawings by the artist best known for painting the ceiling of the Sistine Chapel at the beginning of his career.

The drawing is comparable to others he did dating back to 1490, only one of which, The Greek Philosopher, is held in this country.

Experts say it is a pivotal work because it shows elements of his sculptural cross-hatching style but also the later white ''heightening'' he used to highlight his drawings.

The artist was notoriously reluctant to allow people to look at his drawings, and limited access to them to a close circle of friends.

Only three major drawings by the Renaissance artist, other than those in the Royal collection, are known to be in private hands.

The Mourning Woman was discovered by expert James Miller, who was updating the castle's inventory of art and was killing time in the library.

His colleague, Julien Stock, said: "He was hoping it was going to be full of English watercolours.

But it was old masters, so he called me over.

"I sighed, thinking it was more work. But I soon changed my tune. I was taken aback. I swore. I couldn't believe it.

"Mr Howard didn't really believe it either, although he wanted to. I would never have thought I would find a Michelangelo of this importance."