Fascinating Ending

CAME across this exciting endgame in 500 Master Games Of Chess by Savielly Tartakower and Julius du Mont. Notes in italics are algebraicised from the book.

White to make his 28th move in Sir George Thomas - Alexander Alekhine, Hastings 1933-4

Although a simplified endgame is reached, there are still many problems to be solved.
Black has more space on the queenside, and has the chance to invade White's position there on the light squares. However, Black's bishop is semi-bad in that his central pawn is on a dark square. In addition, the combination of queen-and-knight can sometimes outplay a queen-and-bishop, although here the knight has no outpost (Black will be able to keep it out of f5) or obvious targets.
The analysis engines Komodo10 and Stockfish10 reckon the position is equal.
28.Qd3
Occupying the open file, and solidifying the queenside in that a later ...Qb3 would no longer attack two en-prise men.
28...Bg5 29.Ne3
Heading for f5.
29...g6
Black has an easy draw with 29...Qxe3, but the world champion wants more.
30.Kh2
As a rule, kings are safest when snug against their defensive pawn-wall. An added factor here is that White wants to remove the danger of Black creating threats with a back-rank check.
30...Qb3
An expedition which must be taken seriously.
31.Qe2!?
It may have been better to threaten an exchange of queens with 31.Qc2, or avoid an exchange of minor pieces with 31.Nd1.
31...h5
The engines give 31...Bf4+!? 32.Kg1 Bxe3 33.fxe3, when Stockfish10 reckons Black is winning, but Komodo10's assessment of a slight edge to Black seems closer to the truth.
32.g3 h4
The engines still much prefer ...Bxe3.
33.gxh4
Countering his opponent's plans by … falling in with them.
33...Bxh4 34.Ng4 Bg5 35.Ne3!?
He prevents 35...Bc1 and avoids the casual trap 35.Nxe5 Bf4+.
The engines prefer 35.Kg2 because, once again, they like Black's chances after ...Bxe3.
35...Qa2 36.Qc2 Qa1 37.Kg2 Qe1
This was Black's last chance to play an effective ...Bxe3, which the engines still reckon gives Black good winning chances. The players clearly felt otherwise.
38.Qd3 Qc1
Playing …Bxe3 here would not have been as significant as before as White replies 39.Qxe3, when 39...Qxe3 gives White doubled pawns, but they would not be so weak with queens off. After 40.fxe3, Stockfish10 reckons Black has the upper hand (Komodo10 gives Black a slight edge), but it is hard to see how Black makes progress.
39.Ng4 Qxb2
White's queenside collapses, but White has counterplay.
40.Qd7 Qxa3
If 40...Qxc3 [then] 41.Qe8+ Kg7 42.Nxe5 etc.
It is hard to guess what Tartakower missed here, since the obvious 42...Qb3 protects f7 and leaves Black dominant on the queenside. A better defence, therefore, seems to be the engines' 41.h4! Bxh4 42.Nh6+ Kg7 43.Nxf7 Qd4 44.Nd6+ Kh6 45.Kh3 Bxf2 46.Nf5+ gxf5 47.Qe6+, when White has a perpetual.
41.Nxe5 Qe7 42.Qxe7 Bxe7 43.Nxc6

Even the end of the ending is furiously contested

An ending with rival pawn-majorities usually favours a bishop over a knight, and this position is no exception. But here this factor is countered to an extent by White having the better king (it can get to the centre, or attack on the kingside, quicker than the black king).
43...Bf6
Tartakower points out that sacing the bishop with 43...a4?? loses as the check 44.Nxe7+ lets the knight bounce back to the queenside with 45.Nd5.
44.Nxa5 Bxc3 45.Nb3 Be5 46.Kf3 Kf8 47.Kg4 Ke7 48.f4 Bc3 49.h4 Kd6 50.h5 gxh5+ 51.Kxh5 b4 52.Kg5 Bg7
Thinking of the defensive.
53.Kf5 Kc6 54.e5 Kd5 55.Na5 Bh6 56.Nb3 Kc4 57.Na5+ Kd3 58.Nb3 Ke3
With a hold on both wings, Black has at last obtained the maximum effectiveness of his forces.
59.Na1
Alone this problem-move saves the situation (59...Bxf4 60.Nc2+).
Alas, this is not the case. 59.Na5 also saves the day, as 59...Bxf4 is met by 60.Nc6 b3 61.Na5 b2 62.Nc4+. The engines also point out 59.e6 fxe6+ 60.Kxe6 Bxf4 61.Kd5 Kd3 62.Nc5+ Kc3 63.Na6! b3 64.Nc5 b2 65.Na4+.
59...Kd3 60.Nb3 Kc2 61.Na5 Kc3 62.Ke4 Bf8 63.f5 ½–½
After 63...b3 64.Nxb3 Kxb3 White will take care not to play 65.e6 f6 etc, but will enforce the peace treaty by 65.f6 Kc4 66.e6 fxe6 67.Ke5 etc.