With the annual Game Fair in progress, and echoes from the eruption of debate about fox-hunting still rumbling, it seems an appropriate moment to consider that survival from our deep past, the hunting instinct.

No doubt many of the people now flocking to Castle Ashby, in Northamptonshire, possess it in some degree; and clearly it smoulders in most of the 100,000 people who poured into Hyde Park for the Countryside Rally on 10 July. Equally obvious is the fact that the instinct has died out in the urban majority who, though happy to eat meat prepared for them by someone else, shrink from the thought of killing beasts or birds.

It is hardly surprising that urban man does not understand us rustics. How, for instance, can someone such as myself positively enjoy shooting beautiful animals like deer?

In me, the hunting instinct seems to have survived against the odds. Nobody could be less bloodthirsty than my father, who has never shot, fished or hunted. My mother and her parents, equally, took no part in field sports.

Had I been brought up in a town, I might have gone some other way. As it was, I grew up on a farm in thickly forested hill country, and as a boy I had only one wish when I escaped from school: to go out into the woods and accompany the gamekeeper on his rounds or, better still, prowl on my own with a single-barrelled 28-bore shotgun.

From the start my principal targets were creatures that my mother could cook for us - rabbits, pigeons and, in winter, the odd pheasant. For me, the main point of shooting was to fill the pot, and that remains so to this day. If I go fishing, I do so in the hope of catching a trout or salmon that will be delicious on the plate. The practice of fishing to put back what you catch - increasingly common in game fishing as well as in coarse angling - strikes me as a waste of time.

As I grew older, my limited aim of filling the pot was reinforced by the knowledge that the countryside needs positive management: that deer, for example, must be selectively culled, for the good of the herd and to prevent excessive damage to farm crops and trees. I therefore have no compunction in shooting them, graceful though they are, and fascinating in their behaviour.

Yet never have I had the slightest desire to inflict pain on any animal. Far from it; my aim has always been to despatch the quarry as cleanly and humanely as possible. Satisfaction comes not (as townies suppose) from slaking one's bloodlust, but from practising one of man's oldest skills with efficiency and precision.

In doing so, I am simply joining forces with nature. The point is that in the country death is omnipresent. Countless creatures depend on killing and eating others for their survival: spiders prey on flies, swifts on airborne insects, thrushes on snails, owls on rats and mice, otters on fish, badgers on earthworms, foxes on beetles and rabbits. Anyone who works in the country sees death every day and, far from being shocked by it, accepts it as the inevitable counterpoint of life.

In this context I think often of Billy Arjan Singh, the big cat specialist who won the gold medal of the World Wildlife Fund for his conservation work. A latter-day Jim Corbett, he was a fierce killer in his youth, renounced shooting in middle age and has spent the past 40 years as a volunteer wildlife warden, fighting to save tigers and leopards from extinction.

When, in the Eighties, tigers began killing humans in his area of northern India, he was obliged to shoot eight or 10 animals that had been declared man-eaters. He did so with a heavy heart, but knowing that somebody had to do the job, and that he could handle it better than anyone else. Born with the urge to hunt, he suppressed it for years, then used it to good effect in a crisis.

Would I shoot a man-eating tiger? If circumstances demanded it, yes. Incomprehensible though it may be to city-dwellers, the very instinct that fired Billy also burns in me.