White to play. This position is a variation from Carlsen-Karjakin, Monaco 2011. Although White is a rook up he only has one move to ensure ­victory. What is it?

Answers to me at The Spectator by Tuesday 25 October or via email to victoria@spectator.co.uk. There is a prize of £20 for the first ­correct answer out of a hat. Please include a postal address and allow six weeks for prize delivery.

Last week’s solution 1 c8Q
Last week’s winner Arawn Charters, Bristol