That weak diagonal! More interesting, perhaps, would have been 21.Re7 Rae8 22.Rxe6! Rxe6 (NOT ...Qxe6??) 23.Bc4 Kg7 24.Bxe6 Qxe6 with a roughly level major piece ending.

The rook on the seventh is a bit of a nuisance for Black. I reckon Black is safe enough. White has the mortgage on the d-file, but he will need to open a second front somewhere to make real progress. That is not looking likely.

I think you might be right, Charles. The rook needs to be opposed at once, but not just any old how. Best seems 22...Rf7 or maybe 22...Rad8 23.Rfd1 Rxd7 24.Rxd7 Rf7 25.Qd1 Kg2. A likely continuation from there would be 26.Rxf7ch Kxf7 27.Qd7ch Kg3 28.Qc8, when although White will pick up the rear b-pawn, the Queen and pawn ending after 28...h5 (28...Qxc3 is a bit risky) 29.Qxb7 Qc5 would just about be a guaranteed draw.

if 23. Qd1 Qxc4 24. Qh5 then Rf7 is similar to the game. White picks up the g5 pawn but black is still in the game.

23.Qd1!! Then 23...Qxc4 is unplayable on account of 24.Qh5, winning! ********Response to CH *********** 23.Qd1! Qxc4? 24.Qh5 Rf7 25.Qxg5ch ... [A] 25...Kh8 26.Rd8ch Rxd8 27.Qxd8ch Kg7 28.Qg5ch Kh8 29.Rd1! and Black has no good way to stop 29.Rd8ch; e.g. 28...Rf8 29.Rd7 Qg8 30.Qe7 ... threatens 31.Qe5. Having to protect h7, g7, f6 and f8 already, this extra weak spot (e5) is too much for Black's overworked pieces (30...Re8 31.Qf6ch and mates next move). [B] 25...Kf8 26.Rd8ch Rxd8 27.Qxd8ch Kg7 28.Qg5ch Kf8 29.Rd1 ... with the same result. This was the single moment in which White might have had a winning chance in this game.

23...Rad8 seems right. But that move would not have been available after 23.Qd1.

"25...Kh8 26.Rd8ch Rxd8 27. Qxd8ch Kg7 28. Qg5ch Kh8 29. Rd1! and Black has no good way to stop 30.Rd8ch" What about 29.... Rf8 and if 30. Rd7 Qg8 when 31. Qxg8+ Kxg8 32. Rxc7 Rf7 is looking very level again...

White has better winning chances with the queens on I would have thought.

Yes, this might have been where white had a winning game and turned it into a unwinning advantage....