<The one that got away>

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Black just played:

21...Bd6? <understandable; it clears the 7th rank so that Rd7 guards g7, which frees black's bishop to threaten ...Bxf5, but it give white a pretty chance to win...>

22.R5f2! <uncovering a pin of the black rooks, AND we threaten 23.Qe6+ Kh8 24.Rf7+ Rxf7 25.Rxf7#> Rcc7 <guards the other rook, and Qe6+ can be answered by ...Bf7; but it leaves the 8th rank unguarded>

23.Be5! <threat to capture or deflect the bishop, which is guarding against ...Rf8#> Qb6 <guards bishop>

24.Bxd6 <threatens Rf8#> Qxd6 <recaptures while maintaining protection of f8 square>

25.Qe6+! <queen cannot be taken as ...Qxe6 leaves f8 unguarded, allowing Rf8#> Bf7 <no choice: Kh8 loses to Rf8+, and Rf7 drops the queen to Qxd6>

26.Rxf7 <threat: 27.Rxd7+ Qxe6 28.Rd8+ Qe8 29.Rxe8#> Rxd7 <only choice; guarding the 8th rank with a rook (e.g. ...Rc8) fails because it's answered by Rf8# (note the double-check!)>

27.Qxd6 <winning the queen, and still threatens mate after Qd8+>

And white wins easily (granted, all this would have been tough to see). Unfortunately, white played 22.Rg5?, letting it get away.

On move 21, black's better move was probably 21...Rdc7, where 22.Rf2 is answered by 22...Rc6 (guarding against Qe6+).

<The one that DID win for white>

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This was the position after 45.e4. The black king is preventing white's b-pawn from advancing, but black can't allow the d and e pawns from advancing.

With this position, black played:
45...Re1? <Threatening the e-pawn was a good idea, but NOT while it's guarded by the king. It merely gave white time to play...>

46.Bb4! <attacking the rook, and more to the point, guarding the e1 square> Rb1 <attacking the bishop>

47.Kc4! <the king, now relieved from guarding the e4 pawn, and can guard the bishop> Rc1+ <Black can only give check>

48.Kb5 <king now safe from checks, and threatening e5 & e6> Rd1 <prevents e5>

49.d6! <this pawn now guards c7, thus creating the threat of b7 and promotion> Kc8 <hoping to stop it>

50.Kc6 <and there's no stopping both pawns>

Back on move 45, black should have played 45...Rd1+! driving the king away from the defense of the e-pawn.

If 46.Ke2, then 46...Rc1 and it proceeds to attack the bishop. If 47.Bb4 Rb1 48.Bd4 g5 49.e6+ Ke7 and white makes no progress.