Frustration

ONE of the (many) frustrations of club-level chess is that even if players manage to produce a tense and interesting position, one, or both, will spoil everything by overlooking an obvious threat.
So it was this afternoon in my round-five game at the South Wales International.

White to make his 18th move in David J Williams (1519) - Spanton (1900)

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White has the bishop-pair and more space in the centre. But he has weak kingside pawns, and because of them his king is definitely the less-safe monarch.
Black's pieces are more active, especially when compared with the white knight and queen's rook, and he is starting to menace White's kingside.
My main analysis engines, Stockfish10 and Komodo9, reckon best play is 18.exf5 exf5 19.Nb4, when White has four isolated pawns, two of which are doubled. Black is then slightly better, according to Stockfish10, but Komodo9 assesses the position as fairly even.
However, the game saw:
18.Kh1?? f4 19.d5 fxe3 20.Qxe3
Even worse is 20.Bxe6? Qxe6 or 20.dxc6? exd2 etc.
20...Nd8 (0-1, 31 moves)