Breunor: As Goodevens said:
1) +3.28 (20 ply) 26.Bxh7+ Kf8 27.Nxd4 cxd4 28.Qh5 f6 29.Nb5 Qg7 30.Nxd4 Be7 31.Nf5 Rxf5 32.Rxf5 Rd8 33.a3 Bc8 34.Rff1 Ba6 35.Bd3 Bxd3 36.Rxd3 Kg8 37.Rf5 Qf7 38.Qh6 Qg7 39.Qxg7+ Kxg7 40.Kg2
We see that starting with white's 26, White misses his best move and goes from a +3 to even over 3 - 4 moves:
After 26 Nd4 white is still better but is not necessarily 'winning':
1) +1.37 (22 ply) 26...cxd4 27.Nb5 Qe7 28.Rdf1 f6 29.d6 Qg7 30.Re2 Rxe2 31.Qxe2 Qf7 32.Bc4 Bd5 33.b3 Bxc4 34.bxc4 d3 35.Qxd3 a6 36.Nc3 Rc8 37.Nd5 Kg7 38.h4 Qg6 39.d7 Rc5 40.Qxg6+ Kxg6 41.hxg5 fxg5
Best was 27 Nb5:
1) +1.30 (20 ply) 27.Nb5 Qe7 28.Nxd4 Bxd5 29.Nf3 Bxf3 30.Qxf3 Rc8 31.Qh5 f6 32.Rxf6 Qxf6 33.Qxh7+ Kf8 34.Rf1 Rc1 35.Qh8+ Kf7 36.Qh5+ Kg7 37.Rxc1 Qh6 38.Qf3 Qf6 39.Qb7+ Qe7 40.Qxe7+ Bxe7 41.Rc7 Re3
But after 27 Q x d4 white's advantage starts to diminish:
1) +0.68 (19 ply) 27...f6 28.d6 Qd7 29.Bb5 Qc8 30.d7 Qc7 31.Qc4+ Kg7 32.Qxc7 Bxc7 33.Bc4 Rd8 34.Nb5 Rc5 35.Nxc7 Rxc7 36.Be6 Rc5 37.Re1 h6 38.b4 Rc7 39.Bg4 Rdxd7 40.Bxd7 Rxd7 41.b5
Missing 28 d6! costs white any advantage:
1) +0.16 (22 ply) 28...b5 29.Be6+ Kh8 30.Nxb5 Qb6 31.Qb4 Kg7 32.Qc4 Be7 33.Qc7 Qxc7 34.Nxc7 Rd8 35.b4 Bd6 36.Rc2 Kg6 37.Rc4 h5 38.a4 Bc8 39.Rdc1 Bxe6 40.dxe6 h4 41.Kf2 hxg3+ 42.hxg3
He starts losing with 30 Rfd1:
1) -1.49 (19 ply) 30...Qb6 31.Qg4 Be7 32.b4 Rf8 33.a3 f5 34.Qd1 f4 35.Ne2 Rxe6 36.dxe6 Qc6 37.Rf3 g4 38.Nd4 Qd5 39.Nf5+ Rxf5 40.Qxd5 Bxd5 41.Rxf4 Rxf4 42.gxf4 Bd8 43.f5 Bb6+ 44.Rf2 Bxf2+ 45.Kxf2
30 Ne4 maintains equality:
1) +0.08 (21 ply) 30...Qc4 31.Qxc4 bxc4 32.Nd6 Ba6 33.Rc2 Rb8 34.h4 Bb6+ 35.Kh1 h5 36.a3 Bc5 37.Nxc4 Bxc4 38.Rxc4 Bf2 39.g4 hxg4 40.hxg5 Rxg5 41.Rxg4 Rxg4 42.Bxg4 Rxb2
After 34 Nxb5 white is totally lost:
1) -6.73 (26 ply) 34...Qd5 35.Rf3 Bb6+ 36.Kg2 Bc5 37.Qc3 g4 38.Nc7 gxf3+ 39.Rxf3 Qxf3+ 40.Qxf3 Bxf3+ 41.Kxf3 Rc8 42.Nd5 Kf7 43.a3 Bd4 44.b3 Rc2 45.Ke4 Bc5 46.b4 Bd6 47.Ne3 Rxh2 48.g4 Ra2 49.Nc4 Bc7 50.Kd5 Bg3
Instead 34 Re2 keeps him in a difficult game:
1) -1.37 (24 ply) 34...Bb6+ 35.Rff2 Qc6 36.Re7+ Kg6 37.Qe4+ Qxe4 38.Nxe4 Bxe4 39.Rxe4 Rc8 40.Re2 h5 41.Kg2 Bxf2 42.Rxf2 a5 43.Kf3 a4 44.Ke4 Rc4+ 45.Kd3 h4 46.gxh4 Rxh4 47.Ke3 b4 48.Rd2 a3 49.bxa3 Rh3+ 50.Ke4 Rxa3
So an interesting story. I usually deride the idea that a player can match a computer, but a player of Rapport's strength doesn't usually get such a string of bad moves.