This enormous (each page, made of vellum, must be 1m high) prayer /song book is stored in Chichester Cathedral. There is a typed up info sheet (that I wish I'd photographed ) that says something about it being restored in the 1950s, but there was not a date for how old it is. Can't find any info about it on Google or the cathedral's website. Anyway here for July words.
@josiegilbert I'd love to see more of it.