21. PxB P-K4 22. Q-Kt4 PxP 23. QxP Kt-K3 24. Q-K5
This delays the fatal advance of the QP for one move.
24. … P-QKt4 25. P-QKt3 P-Q5 26. Kt-K4 P-Q6 27. R-Q2 Kt-Q5 28. R-QB1 Kt-B7 29. Q-Kt2 Kt-R6ch 30. K-R1 Kt-B7ch 31. K-Kt1 Kt-R6ch 32. K-R1 Kt-B7ch 33. K-Kt1
Diag. 154
Black does not play for a draw, but only wishes to gain time.
33. … R-QB3
The intention is to double Rooks and to force an entry at B7. P- Kt5 would not be good. The White Rook would no longer be attacked, and the Knight could attack the QP.
34. R(B1)-Q1 KR-QB1
Now that the White Rook has left the QB file, one Rook would be sufficient to force an entry at B7, and Kt-R6ch followed by P-Kt5 could have been played at once, e.g. 34. … Kt-R6ch; 35. K-R1, P-Kt5 (preventing P-QKt4); 36. Kt-B2,R-B7; 37. RxR, PxR; 38. R- QB1, Q-Kt3; 39. Kt-K4, R-Q8 followed by RxRch, Q-Q5ch and P-B8 mate.