Annotated chess game

This is aimless. On e1, the queen covers the third rank squares. Keep that for the moment and see what the rooks can do. As the d7 rook can slide easily from side to side, I'd look to the other, less involved rook, to wit; 51.Rb4ch. The King has but one move, to g5, and there, the second rank rook can come into play. So, the finish might look like this: 51....Rb4ch 52.Kg5 Rg7ch 53.Kh6 ... (No good is 53.Kf6 owing to 53...Qe7#.) 53... Qe3ch (53...Rb6 leads also yo a checkmate, just as quickly) 54.f4 Qxf4ch 55.Qg5 Qxg5#.

Qg1+ is very strong as white as to give up his queen to prevent immediate mate.

Somewhere around here, White could have claimed a draw by three-fold repetition of the position.

Good: cutting out the repetition. White best move is 55.Qg4 to lose the queen, otherwise it is mate in at most 2 moves.

No: the queen was already covering important squares. Move the piece that for the moment is doing the least useful work. What is that b5-rook doing? Diddly-squat. Move it. As it happens, 35...Rb2 would have been checkmate!

Only move. He was never going to invite mate in one by moving to the back rank.

56...Rb3ch - again, bringing in the least busy piece.

67...Rb2#

Breaks the repetition, but - was about to say 'at cost of tangling up your own pieces', but in fact that turns out to be a very good square for the queen. Of course, bear in mind that 69...Rb2# ended the game forthwith.

Although this releases the g-file, it can get back soon enough if needed there.