Bad Loss

LOST rather feebly to a much-lower rated player today in round five of the Highlands Open in Trebic, Czech Rep.

White to play and avoid defeat in Spanton (1923) - Sylwester Grabraczyk (1782)

Despite Black having the bishop-pair, White is only a little worse after a consolidating move such as 30.Ra3 or 30.Rba1.
Instead, I played 30.Kf1, which effectively loses on the spot.
Can you find Black's game-winning idea?
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Black played 30...Bxe3 31.Nxe3 Rxe3! 32.fxe3 Bxc2 33.Rab4 Bxb1 34.Rxb1
Black has won a pawn and cannot be prevented from winning the b5 pawn (0-1, 48 moves)