The series was only named “The Constable Twitten Mysteries” after I’d written this first book, so Twitten is not the protagonist as much here as he is in the later books, once we’d decided on the series title. It was my editor’s idea that the revelation in this book of Mrs Groynes’s true character – criminal mastermind posing as simple cockney charlady – should be deferred to mid-way through the book, which I’m sure added narrative tension, but meant it was impossible to promote the book without committing the unforgivable sin of “spoiling”. Anyway, I’m spoiling it here and I don’t care. Watch out for Mrs Groynes!

A couple of points of interest: the “Middle Street Massacre” of 1951 was invented by me. I have seen references to it on the internet as if it really happened, but it didn’t. The name Miss Sibert comes from my favourite junior school teacher at the Orchard School in Petersham in the 1960s.