The original was a collaboration between Shakespeare and John Fletcher, his successor as house playwright to the King’s Men company. It was performed twice in 1613 but never made it into print and was lost to history.
Theobald claimed, more than a century later, to have had three copies of the play, which were also subsequently lost, on which he based his adaptation.
Double Falsehood was declared a hoax soon after it opened and disappeared, although Theobald became a famous editor of the playwright.
However, after 10 years’ research, Brean Hammond, professor of Modern English Literature at Nottingham University, believes he has found proof of its authenticity from historical evidence and analysis of the text.
“It’s impossible to compare Double Falsehood with Cardenio because those manuscripts have been lost,” he said.
“But if you look inside the text there is the presence of three hands at work, Shakespeare, his collaborator John Fletcher and Theobald.”
Some words in Double Falsehood were not in any of Theobald or Fletcher’s other works, he said.
“A small example is the word ‘absonant’ which appears in the first act of Double Falsehood. It means displeasing to the ear, harsh or discordant.
“This word does not appear in Theobald or Fletcher’s work but it does appear to be a word that was invented by Shakespeare.”