However, as midnight approached, he turned to the devil and asked for help, and offered his soul in exchange for being able to finish the book.

The whopping book is 36 ins tall and weighs 165lbs (Picture: Getty)

The devil agreed, and even signed the work by adding a self-portrait of himself.

Although the story sounds like something from a horror film, its authenticity was given a boost by a National Geographic report which revealed that handwriting analysis had suggested that a single scribe had composed the entire manuscript.

And a ‘hermann inclusis’ signature in the text suggests that there was only a single author.

The book’s contents also seem in keeping with the legend, as it contains five long texts along with the complete bible.

But some researchers have rubbished the story, and instead claim that it was created by a monk who decided to devote his work to the text.

You can read a digitised version of the book here, but we won’t be held responsible for any subsequent demonic possessions.