In the position below, it's Black to play. But that's not the question. Instead, it's what was White's last move? And when you've solved that (it is possible!), what were the three previous half-moves (B/W/B)?:
When all four problems have been published (by Sunday), send in your answers to me. The best set of answers will win a book prize.
Sad news received today... Peter Keffler has died, aged 92. There will be a proper tribute to him after Christmas.