A portrait believed to be the only surving portrait of William Shakespeare painted in his lifetime could be the 17th century courtier Sir Thomas Overbury, an expert believes.

Painting believed to be Shakespeare could be Sir Thomas Overbury

The Jacobean painting from the family collection of art restorer Alec Cobbe was thought to be the bard because it closely resembled the engraving in Shakespeare's First Folio.

It is also noticeably similar to another painting believed to be the playwright owned by the Folger Shakespeare Library in Washington, DC.

But now experts believe the elaborate lace collar and gold embroided doublet are too grand for the playwright.

Dr Tarnya Cooper, the sixteenth-century curator at the National Portrait Gallery in London, believes the portrait bears a greater likeness to Sir Thomas Ovebury.

She told The Times: “if anything, both works, the Folger and Cobbe portraits, are more likely to represent the courtier Sir Thomas Overbury”.

An authentic portrait of Sir Thomas Overbury (1581–1613) was bequeathed to the Bodleian Library in Oxford in 1740 and bears a close likeness to the Cobbe painting.

In both pictures the sitter bears distincitve marks such as a bushy hairline and a slightly disformed left ear.

Overbury was an English poet and essayist. He was sent to the Tower of London in 1613 by James 1 after refusing to become ambassador to the court of Michael of Russia. Within five months of imprisonment he had been poisoned and died in September 1613.

The Cobbe portrait is thought to have been painted in 1610 - six years before Shakespeare's death - when he was about 46 years old.

It remained in the same family for centuries and was inherited by Mr Cobbe. In 2006, he visited the National Portrait Gallery and saw the Folger painting which was on loan from the Washington library.

Mr Cobbe saw the painting and realised the similarities with the painting he had inherited.

Believing his painting to be the original, he contacted Professor Stanley Wells, chairman of The Shakespeare Birthplace Trust.

Prof Wells said: "My first impression was scepticism - I am a scholar. But my excitement has grown with the amount of evidence about the painting.

"I am willing to go 90 per cent of the way to declaring my confirmation that this is the only life time portrait of Shakespeare. It marks a major development in the history of Shakespearian portraiture."

The painting will go on display at The Shakespeare Birthplace Trust in Stratford-upon-Avon on April 23, Shakespeare's birthday.