It appears to be written in an Anglo-Saxon unical, with Latin interspersed.
The image below is from the Book of Kells, and provides a more elegant example of unical:
The reason i believe it may be Anglo-Saxon, is the use of the letter thorn (Ƿ, ƿ)--but that could also mean that the document comes from Old Norse or Icelandic. However, unical script was falling into disuse by the time Christianity (and therefore Latin) reached the Norse and the Icelanders, so that is why i suspect it is from an Anglo-Saxon source. Olaf Tryggvasson forced the Norse to convert to Christianity, including the population of Iceland, and he committed suicide in 1000 AD. Unical had already fallen into disuse by then.