A portrait said to be the only signed and dated image of William Shakespeare created during his lifetime has gone on display in London.

Its owner, who wishes to remain anonymous, is offering the piece for sale by private treaty – without an auction – for a figure of more than £10 million.

It is the work of Robert Peake, Sergeant-Painter to King James I, and is signed and dated 1608.

Prior to 1975, the picture hung in the library of a stately home in the north of England, once home to the Danby family. Since then it has been in private ownership.

Those behind its sale claim the the connections between Shakespeare and Peake are “extensive”.

They say Peake was regularly commissioned to paint the portraits of high-ranking members of the Court and Jacobean society.

They also noted he was commissioned by the Office of the Revels, which oversaw the presentation of plays, and worked in the premises in Clerkenwell, London, where some of Shakespeare’s plays were rehearsed.

However, only two paintings of Shakespeare, both posthumous, are generally recognised as valid – the engraving that appears on the title page of the First Folio, published in 1623, and the sculpture at his funeral monument in Stratford-upon-Avon. Shakespeare died in 1616, at the age of 52.

Art expert Duncan Phillips, who investigated the work ahead of the sale, said: “There is more evidence for this portrait of Shakespeare than any other known painting of the playwright.

“It is a monogrammed and dated work by a portrait painter of serious status with connections to the artist who produced the image for the First Folio.

“The picture has survived the past 400 years almost untouched by wear and tear thanks to its ownership by a family of Shakespeare enthusiasts who hung it in their library.”

However, Shakespeare expert Michael Dobson told the Daily Mail claims the painting is of the Bard are “wishful thinking”.

The painting went on display on Wednesday at Grosvenor House Hotel, London.