A portrait which was widely thought to be that of William Shakespeare is not the Bard after all, the National Portrait Gallery said today.

The Grafton Portrait has become one of the most iconic images of Shakespeare, gracing the covers of numerous books about the playwright.

The image of a man in the first flush of youth has fuelled the Shakepeare in Love-type theories about the life of the great writer.

Now, after nine months of research and restoration work, the National Portrait Gallery has announced that it has found no evidence to support the view that the portrait is of Shakespeare.

It confirmed through scientific investigation that the portrait, painted in oils by an anonymous artist, dates back to 1588, when Shakespeare would have been 24.

The inscription on the top of the painting records the age of 24 with the date 1588, making the sitter an exact contemporary of Shakespeare.

But gallery experts say Shakespeare was about to join a travelling theatre troupe at the age of 24, after becoming a father to twins, and was unlikely to have been able to afford the style of dress seen in the portrait.

The portrait, on loan from the John Rylands Library in Manchester, depicts a youth with curly brown hair and grey eyes, wearing a sumptuous scarlet jacket worn by European men between the 15th and 17th centuries.