Experts are "lost for words" to have found that a medieval prayer book has yielded yet another key ancient text buried within its parchment.

Works by mathematician Archimedes and the politician Hyperides had already been found buried within the book, known as the Archimedes Palimpsest.

But now advanced imaging technology has revealed a third text -- a commentary on the philosopher Aristotle.

Project director William Noel called it a "sensational find".

The prayer book was written in the 13th Century by a scribe called John Myronas.

But instead of using fresh parchment for his work, he employed pages from five existing books...