STUDENTS researching for a display of Tudor portraits have uncovered a "ghost figure" of the Earl of Southampton - Shakespeare's only known patron.

The figure may be Henry Wriothesley, 3rd Earl of Southampton, who lived at Place House, formerly Titchfield Abbey.

He was Shakespeare's "man of the sonnets" the National Portrait Gallery, which has the portrait in its Tudor collection, said.

It was painted over with an image of his wife Elizabeth Vernon, who was a maid of honour to Queen Elizabeth I.

The unknown artist portrays her aged in her 40s, wearing a black dress slashed to reveal scarlet fabric.

The secret portrait was found when it was X-rayed for a display at Montacute House, Somerset, a National Trust property and a regional partner of the National Portrait Gallery.

The male figure, which is lower and to the right of the existing portrait, closely resembles the composition of portraits of Wriothesley made around the same time, some of which have been attributed to the Dutch artist Paul van Somer, the National Portrait Gallery said.

The display was curated by students from Bristol University.

A spokesman for the National Portrait Gallery said: "It is thought that the unknown artist of this portrait painted over the image, possibly because a commission for a double portrait of husband and wife was abandoned in favour of the single portrait seen today.

"Another very similar version of this portrait, attributed to van Somer, exists at Sherborne Castle, Dorset, very close to Montacute House, where this portrait can now be seen."

A favourite of Elizabeth I, Wriothesley (1573 -1624) was the only known patron of Shakespeare, who dedicated his poem Venus and Adonis to him.

But his tempestuous relationship with the Queen culminated in his involvement in a rebellion in 1601.

Condemned to death when the rebellion failed, his punishment was commuted to life imprisonment and he was released by James I.

He was known at court for his flamboyant appearance, particularly his long auburn hair.

The portraits can be seen in the display On the Nature of Women: Tudor and Jacobean Portraiture 1535-1620, April 30 to October 2009, Montacute House, Somerset.

Other discoveries in the display include a portrait thought to be of Margaret Douglas, Countess of Lennox, who was Mary Queen of Scots' mother-in-law and one thought to be of Lady Jane Grey, both of which have not been seen in public for more than 70 years.