That grand old man Viktor Korchnoi, now 65, is still producing games of great imagination and vitality. Indeed, his style has, if anything, become more exciting as he gets older. In his most successful years, he had such faith in the inherent defensibility of most positions that he seemed inherently reluctant to launch an attack. He would do so only after the most complete and cumbersome build-up.

Another top grandmaster once likened Korchnoi's attacking style to a cripple stumbling towards you swinging his crutches. As long as you remembered to side-step in time, you would be fine, but he could do you a terrible injury if you failed to get out of the way. Nowadays, with the impatience of old age creeping up on him, Korchnoi attacks more freely, as this game from Wijk aan Zee demonstrates.

The central push with 4.f3 and 5.e4 is just the sort of space-gaining strategy one expects of Korchnoi, though in his youth he used to leave such things until the late middle-game. Having succeeded in acquiring a potentially mobile pawn centre with 19.f4, one would have expected him to manoeuvre his rooks carefully - to f1 and e1, perhaps - then put a bishop on d3 and slowly prepare a decisive push with e5.

That, however, is not the style of Korchnoi the pensioner-prodigy. It's full speed ahead with 20.Rg1 and 21.e5! aiming for the weakness at g6. The energetic finish with its temporary queen sacrifice is delightful too. After 34...Rd4 35.Nf6 White wins easily.

White: Viktor Korchnoi

Black: Vladimir Onischuk

1 c4 f5 18 cxb5 axb5

2 Nc3 Nf6 19 f4 Qf7

3 d4 g6 20 Rg1 Bd4

4 f3 Bg7 21 e5 Nxe5

5 e4 fxe4 22 fxe5 Bf5

6 fxe4 d6 23 Bd3 Bxd3

7 Nf3 0-0 24 Qxd3 Bxg1

8 Be2 c5 25 Rxg1 Kh7

9 d5 Ng4 26 bxc5 dxc5

10 0-0 Ne5 27 Ne4 Qf5

11 Bg5 Nbd7 28 Qe3 Qh5

12 Kh1 h6 29 d6 Rf3

13 Bd2 a6 30 dxe7 Rxe3

14 Qc2 Rb8 31 Nf6+ Kh8

15 a3 Qe8 32 Nxh5 Rd3

16 b4 Nxf3 33 Rxg6 Rxd2

17 gxf3 b5 34 Rd6 resigns

After four rounds at Wijk aan Zee, Piket (Netherlands) leads with 3 points, half a point ahead of Yermolinsky (US) and Sokolov (Bosnia). Nigel Short has 2 points.