Norman Williamson, the Gold Cup winner in 1995, provides an armchair guide over the jumps: Cheltenham festival

TO WIN a Gold Cup, a horse not only needs class and stamina but also balance and cleverness, all the hallmarks of a top-class staying chaser. The pace at which the race is run, the contours of the track and the steep climb to the finish will ruthlessly expose any weaknesses. For the rider, the course is a test of jockeyship as well as horsemanship, full of pitfalls for the unwary or inexperienced.

On the big day, the atmosphere is electric as the horses walk round at the start. Norman Williamson, hero of the race two years ago on Master Oats and aboard Unguided Missile on Thursday, says: "Everyone knows this is finally it. Ideally you want to come to the first fence in front, to give your horse a good view, and then lie fourth or fifth. It's better to be on the inside of the field if you can. Cheltenham is a sharper track than many people think; you're on the turn the whole way, and you can gain a lot of ground by following the rail."

The first problem fence is the third, approached on a downhill run. Williamson explains: "When you turn the bend you can't believe how the ground drops away, and the horses are still a bit fresh. Then it all settles down a bit and you can take up the position you want."

The open ditches were altered two years ago to reduce the size of the sloping apron, which had tended to check exaggeratedly horses who dragged their hind legs through the fence. The uphill ditch poses its own peculiar problem. "Perhaps it's because the horses can see the rising ground behind the fence, and that alters their view of it," he says. "The trick is not to meet it short - a long stride is better."

The fence after the turn from the top of the hill needs care. Williamson says: "You're meeting it just off the bend, and the horses get keen again. Master Oats nearly fell there."

Television tends to flatten all sport, and racing is no exception. The gradients at Cheltenham are steeper than they look on the screen and the downhill run back towards the stands is no place for the faint-hearted. Over the years the plain fence on this stretch has provided plenty of incident, particularly second time round with horses beginning to come under pressure. Six years ago, however, the pronounced fall-away on the landing side was modified. "It's not too bad now," says Williamson. "And the ground levels out just before the fence so it's a good approach."

With one circuit to go, the race begins to take shape. "By the time you get back to the stands again you have a good idea of your fate. Ideally, you'll establish a rhythm from the start, jump adequately on the first circuit and save any big leaps for the second, so your horse does not use up his energy. But the speed is a factor; you're going that half-stride faster than usual, because you're in top company."

Good jumping and positioning on the second circuit is crucial. "As you go out into the country you want to be travelling, as you don't want to be scrambling after something down the hill. You're racing now, and after the water you really must jump everything. If you miss a beat you're in trouble; one of the golden rules is not to make up ground going uphill. Master Oats absolutely winged the last ditch."

Many a drama has been played out on the gruelling run up the hill to the winning post. Williamson adds: "The temptation is to go for home from turn into the straight, but to the line it's a lot longer from there on the Gold Cup course than you think. You need courage from the horse and judgement from the jockey, and determination from both."