Academics at Oxford University believe that William Shakespeare worked with a co-author when writing All's Well That Ends Well.
Just days after the Bard's birthday, the new study claims that one of his contemporaries, playwright Thomas Middleton, is the most likely collaborator after examining inconsistency in the play's text.
Rhyming patterns, grammar and specific words were all put under the microscope by Professor Laurie Maguire and Dr Emma Smith of the university's English department.
Maguire told the BBC that the word 'ruttish', for example, which means lustful, only appears at that time in a separate work by Middleton.
She said she is 'very confident' that theory is correct, and claimed that the majority of plays from Shakespeare's era were collaborative.
The theory will no doubt interest conspiracy theorists who since midway through the 19th Century have questioned the authorship of Shakespeare's plays.
One of the longest-running and divisive topics in literature, sceptics over the years have tried to discredit Shakespeare with more than 70 different candidates, including the aristocrat Sir Walter Raleigh and dramatist Christopher Marlowe.
Last year saw the release of Anonymous, a major film starring Rhys Ifans that was based on the theory that Shakespeare's play were actually written by Edward de Vere, the Lord of Oxford - a theory based on the popular idea that Shakespeare would have been too uneducated to produce many of the cultural and classical references in his work.
The concept of co-authorship may seem a more moderate theory, but it is not a new one.
In fact, the first time Shakespeare's authorship was openly questioned was by a Joseph C Hart, who also believed there were other hands at work in the plays.
In his 1848 book The Romance of Yachting, Hart claimed that Shakespeare merely adapted the works of more educated playwrights to make them popular for the stage, and that his only original contribution were the crude jokes sometimes deployed by his characters.