The Rafaels house is actually Benham Valence near Newbury, Bucks. Which was in the process of being restored to its full glory by Norsk Data Ltd. Who purchased it as their UK head office during the 1980's (and who I was working for at the time). I have always admired Joan Hickson in the role of Miss Marple in this series and was disappointed that she didn't receive more accolades for her work.
Review of Miss Marple: Nemesis
