For the last few years, I’ve worked with an Air Arms S200 pre-charged pneumatic air rifle propped against my desk. It began as a precaution against mice, who’d taken advantage of the decreasing faculties of my aging and incontinent three-legged cat by nesting in her cat litter, popping out now and then to go on brazen runs across the floor. I soon learnt that air rifles are not much use against mice, which are generally too speedy and cautious to be shot. By the time I gave in I’d made many tiny holes in my skirting board.

But the rifle stayed, and every so often I’d pick it up and take pot shots at the squirrels that scurried in the trees at the end of my garden. I’d write with one eye on the trees, looking out for the tell-tale rustle of twigs and leaves that would announce the coming of the hordes from their dreys high in the leylandii further down the street. The grey squirrel, Sciurus carolinensis, is not a native species, and I told myself these brutal afternoon slayings were merely good environmental management: squirrels are pests, disturbing nesting birds, eating their eggs and their young, and gnawing the bark off the branches of trees. They’re also scatter-hoarders, making several thousand caches of food each season, digging up bulbs and young plants as they go.

Shooting squirrels is legal. Indeed, if you catch a grey squirrel in a trap then you’re legally obliged to kill it, but you have to be careful. A tap on the skull with a blunt instrument or a headshot from a trained professional (whatever that might be) are the only acceptable methods. Last year Raymond Elliot, a window cleaner from Staffordshire, was fined £1,547 and given a conditional discharge for causing ‘unnecessary suffering’ by drowning a squirrel he’d caught in a trap, not knowing what else to do with it. I prided myself on my five-pence groupings at 15 yards. I used flat-headed .22 pellets (branded ‘Vermin-pell: they pack a punch!’) for better energy transference. I always killed with headshots. Yet I felt guilt in snuffing out these lives. An animal never looks quite as alive as it does when it’s dying. Some would plop out of the trees quite straightforwardly. Others would stage melodramatic death scenes, clinging to the bark and staggering about like mafia dons in their death throes.

The wilds are returning to London. Butterflies prefer the shelter of buddleia sprouting from industrial hulks to the exposed and dangerous hedgerows; salmon and trout leap once again in the Thames, foxes riffle through our bins like desperate hacks. Above, cruising the thermals, peregrine falcons keep watch, nesting on the chimney of the Tate Modern. And along with the animals come the country pursuits, becoming strange parodies of themselves on the way. Most mornings in Trafalgar Square a man flies falcons at the pigeons. On a small patch of scrubland round the corner from my house a row of beehives hums. Eels are returning to the Regent’s Canal, having made the journey from the Sargasso Sea. Occasionally I pull one out and smoke it over oak chips. Mushrooms sprout in secret on Hampstead Heath.

But London’s is a haunted, perverted wildness. The foxes are mangy, and have no natural fear of humans. There are stories of urban crack squirrels, addicted to the drug they dig up from gardens, where dealers leave their stashes: ‘It was ill-looking and its eyes looked bloodshot’, recalls one eyewitness, ‘but it kept on desperately digging. It seems a strange thing to say, but it seemed to know what it was looking for.’ I ate one of the squirrels I’d shot once, out of curiosity. It was difficult to skin, but the meat was firm and subtly flavoured: no hint of the urban diet on which it was raised. The rest I chucked over the fence at the back of my garden when no one was looking. They were taken away in the night, I presumed by foxes on their nocturnal scavenges.

D. H. Lawrence was no fan of what he called the ‘odious little hunter’, and he had reason to be scathing. In the world of guns and fur there is no such thing as a sporting chance, unless you’re a bad shot. ‘They crouch,’ wrote Lawrence in ‘Man is a Hunter’, ‘they lurk, they stand erect, motionless as virile statues, with gun on the alert. Then bang! they have shot something, with an astonishing amount of noise. And then they run, with fierce and predatory strides, to the spot. There is nothing there.’

After I began shooting the squirrels (efficiently, it must be said; ruthlessly), the birds returned to my garden. Two pairs of blackbirds nested this spring, as well as a pair of pigeons, high at the top of the lime tree. I watched for weeks as the fraught blackbirds flitted about to feed their ever-hungry young. I worried as cats prowled and crouched in the undergrowth. One morning I saw a tiny, indignant fledgling standing on the lawn, hunched in on itself like an old man. It had fallen from the nest, and one of its parents was perched in a tree above it, still feeding it, though more nervous than ever.

Cats would come and go, circling, and I threw figs at them to scare them off. The next day I spotted a tiny corpse in the bushes: the half-fledged wings pulled out of themselves, wasps settling on the body. Another lay below the nest, which was now empty. I’ve put my gun away now. The squirrels have moved back in to fill the void.