Puzzle no. 264

White to play. This position is a variation from Alekhine-Hofmeister, Petrograd 1917. A typical Alekhine conclusion. A queen down — how does he force the win? Answers to me at The Spectator by Tuesday 7 May or via email to victoria@spectator.co.uk or by fax on 020 7681 3773. The winner will be the first correct answer out of a hat, and each week I shall be offering a prize of £20. Please include a postal address and allow six weeks for prize delivery.
 
Last week’s solution 1 Rxf7
Last week’s winner Malcolm Burn, Gloucester