Years ago I came upon a hardcover book at a booksale in the basement of a church in Granville Ferry. The novel is entitled Wolf's Castle and was written by William Melvin. It's a really good medieval story and I remember enjoying it. I still have the worn tome but can not find it on GoodReads. If you have read this book, or know another title for it, please let me know. Thanks :)
Still available on Amazon. I read it as a child and loved it. One can still stay at what I believe is the eponymous castle in Scotland (now a B&B and cooking school, on an island with a burn flowing round it). The castle was completely restored by the Fry family and sold to the current owner for a song.