I've read this yesterday and thought the Guardian's title was misleading. If I understood rightly, the chapter found was already known, although it was through a later copy. So this discovery will bring minor changes, which a few scholars will enjoy the most.

The original text from around 1010 is lost. From the copy written before 1240, only 4 chapters, now 5, have been preserved. And all of the 54 chapters are known through later copies from around 1500.