Blunder!

MADE a horrible blunder against the top seed, a junior born in 2003, in round two of the 70th Hampstead U2200.

White to make his 29th move in Spanton (1890/171) - Federico Rocco (2174/211)

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My main analysis engines Stockfish10 and Komodo9 reckon the game is dead equal after 29.Kh2, eg 29...Rc1 30.Qb5, when Black's back rank is just as vulnerable as White's.
Instead I played 29.Qa6?? Black replied 29...Qf4 (29...Rc1+ 30.Kh2 Qf4 is even stronger). White is completely busted. The remaining moves were 30.Qd3 Rc1+ 31.Kh2 Qxh4+ 32.Rh3 Qf4+ 33.Qg3 Qf1 34.Qe3 Re1 35.Qh6 Qg1+ 36.K3 Re3+ 0-1