In last week’s puzzle, posted as a tribute to the late Jonathan Penrose, White won with 14. Rxf7!.

Now 14… Kxf7 loses to 14… Kxf7 15. Qd5+ Kg6 16. Qf5+ Kh5 (16… Kh6 17. h4) 17. g4+ Kh6 18. h4 g6 19. Bxg5+ Kg7 20. Qe5+.

Black correctly played 14… d5, when the simple 15. Rxg7 would have given Penrose a winning advantage. Instead he played 15. Rf2, and, a few moves later, this position appeared on the board.

Here, Black blundered with Kf7, and White won a few moves later. He could have played the spectacular Qxg3+, which, as you’ll see, leads to a perpetual check. Stockfish tells me that O-O-O would also have been equal.