Sometimes you pick up a book in a second-hand bookshop. You have never heard of the writer, but you like the cover, and that is all it takes to send you down a literary rabbit hole.
This is what happened to me a couple of weeks ago when I picked up three detective novels from the 1930s by Christopher St John Sprigg.
At first, Sprigg appears to belong comfortably to the world of Golden Age crime fiction. He wrote ingenious mysteries with titles such as Fatality in Fleet Street, The Perfect Alibi and Death of an Airman.