Missed Opportunity

BENIDORM began this afternoon.

Black to make his 39th move in Daniel Pousada Estevez (1685) - Spanton (1934), U2000 Round 1

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39...bxc4?
Best is 39...Re5+, eg 40.Kd3 g5 41.hxg5 fxg5 42.Rf8 bxc4+ 43.Kxc4 g4, with an easy win for Black.
40.Rxc4 Rb5 41.Rxa4 Rxb2+ 42.Kf3
Black is better, but the position requires care.
42...h5?!
Almost certainly wrong.
Stockfish10 suggests the calmer 42...Rd2 43.Ra5 g6 44.a4 Rd4 45.Ra6+ Ke5 46.Ra5+ Rd5 47.Ra7 h6, when Black is making slow but promising progress.
Komodo10 gives 42...Rb3+ 43.Kf4 h5 44.Ra7 g6 45.Rg7 Rh3 46.Rxg6 Rxh4+ 47.Kg3 Ra4 48.Rh6 Rxa3+, which it assesses as giving Black the upper hand, but the position is a well-known draw.
43.Ra5 g6?!
The engines give 43..Rb3+ 44.Kg2 Rd3 45.Rxh5 Rxa3, but White would seem to have decent drawing chances.
44.Ra6+ Kd5 45.Rxf6 (½–½, 62 moves).
Going back to the position after 44..Ra6+, Black had to try 44...Kf7 45.Ra7+ Kg8 46.Ra8+ Kg7 47.Ra7+ Kh6 48.Ra6 f5, but with very minimal winning chances.