7...c6: Mortimer's 7. c4 was questionable (7. Nc3 looks best), but Mason's 7...c6 made Moritmer's move look good, and bungled up his development. 7...Nc6 was best.

8...f5: Moritmer's 8. Qc2 was inferior to 8. cxd5 or 8. Nc3. Mason should have begun developing his Queen-side with 8... Na6. After the text, Mortimer could have seized a significant advantage with 9. cxd5.

9...NxN: Mason should surely now have begun bringing out his Queen-side pieces with 9...Na6. Exchanging Knights only helped White, who should have responded 10. QxN rather than messing up his pawn structure with 10. bxN (as he did).

10...dxc4: This should have been a losing move. Mason yet again missed a chance to develop his Queen-side with 10...Na6. Had Mortimer followed up 11. Bxc4+ Kh8 properly, the game should have been his.

12. Rd1: Mortimer here missed the powerful advance 12. e6.

13. Rb1: Mortimer should have squelched Mason's Queen-side prospects with 13. a4. (Far batter than the text and far better than the Tournament Book's suggested 13. Bg5).

13...b5: Mason yet again failed to attend to his undeveloped Queen-side. He should have played 13...Nd7.

14. Bd3: Far inferior to 14. Bf1.

14...Qh5: Yet again, Mason should have started developing his Queen-side pieces with 14...Nd7 instead of this misguided Queen move.

15. c4: The beginning of a bad plan that ultimately bore fruit only because of Mason's later misplays. 15. Re1 was best.

16. c5: Continuing with his bad plan. 16. Nd4 was best.

17. Be3: Needlessly blocking the e-file. Mortimer should have played to break up Mason's Queen-side pawns with 17. a3.

18...Be6: Mason finally begins to bring out his Queen-side pieces, but chose the wrong candidate. 18...Na6 was best.

21. Qc4: The wrong spot for the Queen. He should have played 21. Qa4.

The "climax" of the game came after Mason's 23...Ne6. The position was as follows after that move:

click for larger view

Mortimer, whose game had been running downhill since move 10, here played 24. Rd6! While the claim by Rosenthal in the Tournament Book that this move "gives White the superior game," it did present Mason with the unpleasant choice of allowing the Rook to maintain a commanding post on d6 or allowing Mortimer a dangerous passed pawn deep in his territory.

Mason decided, reasonably enough, to win the exchange with 24...BxR. But then Mortimer erred with 25. cxB instead of the clearly better 25. exB.

The balance of the game consists of Mason trying but failing to exploit his material superiority while fending off the dangerous pawn at d6.

Mason had several chances to win, most notably after Mortimer's poor 34. Bb2 (34. Qd5 was best). Mason should have played 34...Nd4 instead of the useless 34...Qf7.

With 36...Rfe8, Mason set a little trap. As Rosenthal point out in the Tournament Book, had Mortimer played 37. Qxa5 Mason would have had a win with 37...Ra8 38. Qb5 Rxa2.

Mortimer avoided this pitfall with 37. Qc4.

With Mason still unable to come up with a plan to capitalize on his exchange plus, a draw was agreed after move 39.