Someone once described chess as the only profession in which clinical paranoia led to improved success. That is quite wrong, of course. There are plenty of professions in which paranoia is, if not an essential qualification, at least a desirable attribute. But there is no denying the value to a grandmaster of a suspicious temperament.

A powerful American player of my acquaintance has the habit of peering from several directions at both his opponent and the pieces as though convinced they are trying to hide something from him.

His expression, similar to that of a mongoose approaching a snake, has induced many an opponent to blush with guilt at making even the most transparent threat. And when you don't even trust your own pieces to behave honestly, it's good insurance against falling into any traps.

In the following game, played in the current world championship zonal tournament in Reykjavik, the Icelandic grandmaster Helgi Olafsson demonstrates the drawbacks of a trusting nature.

There are at least three places in the game where a true, card-carrying paranoiac would not have played as Olafsson did. First, the opening: When White turned the Trompowsky Attack - an opening whose vulgar 2.Bg5 should be treated with great suspicion at the best of times - into a gambit with 5.e4 and 6.Nc3, a true C-CP would scarcely have sniffed twice before declining the offer with 6...e3. Objectively it may not be as good as taking the pawn, but 6...exf3 is so clearly what White wants, it must be good policy to deny him it.

Then there is 14...b5. Why nudge the bishop back to d3, where it is pointing directly at the black king? And having nudged it there, why not pursue it with 15...Nb4.

Finally, we come to White's 18.Rdf1. Only a trusting nature could fail to detect venom in such a devious move. There simply must be some fiendish plot down the f-file, and the next move revealed all. Black had to play 18...h6. As the game went, 19.Bxh7+! and 20.Qh5 brought an abrupt end to proceedings. 20...Nxg5 21.hxg5 f6 22.g6 forces mate and 20...Nhf6 21.Bxf6 Nxf6 22.Rxf6! shows why the rook went to f1.

A nice attack, but Black should have seen it coming a long way off.

White: Sune Berg Hansen

Black: Helgi Olafsson

1 d4 Nf6 11 Bc4 Be7

2 Bg5 Ne4 12 Kb1 0-0

3 Bf4 d5 13 h4 Nd5

4 f3 Nf6 14 Ne4 b5

5 e4 dxe4 15 Bd3 Nd7

6 Nc3 exf3 16 Ng5 N7f6

7 Nxf3 Bg4 17 Be5 a5

8 h3 Bxf3 18 Rdf1 a4

9 Qxf3 c6 19 Bxh7+ Nxh7

10 0-0-0 e6 20 Qh5 resigns

William Hartston