35. ?
In this round 6 game, Gerard O’Connell had fought back from a losing game to reach the diagrammed position. He now saw nothing better than 35. Nxf8, and the game soon ended in a draw.
He could have won via 35. f5!, when Black has no good defence to Re8 followed by Qe6+ / Qe7 and a quick mate:
(I) 35… Rxf5 36. Qe6+ R5f7 37. Re8, or more neatly 37. Qxf7+, etc.
(II) 35… Qh6 36. Re8 Qg5 37. Qe6+ Kh7 38. Rxf8 Rxf8 39. Nxf8+ Kg8 40. Qe8 and wins.