White to play. Mateusz Bartel-Jules Moussard, London Chess Classic 2023. Bartel’s next move yielded a crushing advantage. What did he play? Email answers to chess@spectator.co.uk by Monday 8 January. 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 Ne5!, e.g. 1…dxe5 2 Qd8# or 1…Kxe5 2 Qh8# or 1…d5 2 Ne6# or 1…Nxd3 2 Nef3# or 1…Nc2 2 Ngf3#

Last week’s winner Mike Pitt, Cardiff