Book detectives please
This book is set in an English university probably around the 1900s. It's winter time. The narrator is a professor at this university and has stumbled across some mystery hidden in the old manuscripts. This mystery happened a hundred years prior - a murder?
He is probably in his 60s and an old school chum (?) has come to stay but is an unwelcome visitor. It's coming up to Christmas, snow is falling.
There is reference to a wife the narrator had who left him for another man. He is still bitter about this but over the course of the novel mellows and decides to grant her the divorce.
I'll keep thinking if I can come up with any more details.