I saw the first one last Sunday, silhouetted against a storm-cloud. It looked austere, purposeful, as it scythed through the air in a long arc. Then, another bird appeared and the two of them flew through impossible turns and twists, shrieking all the way. There seemed to be such a heady joy in it, a complete physical mastery that animals have naturally, and that we so rarely attain.

Swifts are the last of their family to arrive from the south, and the first to leave. By the end of July, they will be gone, unlike the laggard swallows and martins who will be around for weeks. When I lived in Chadwell Heath, out in the distant reaches of Greater London, they nested under the eaves of the 1930’s houses, returning to the same place every year. When it was humid, they would roll through the garden just a metre or so above the lawn, a rumble-tumble gang of squealing hooligans scooping up the mosquitoes that were rising from the ground.

On cooler days I would lie on my back and watch them as they swirled and circled hundreds of metres above my head. Once I studied them for so long that the whole world became inverted, as if I was looking into the sea and gazing on tiny fish rather than looking up. The effect was so disorientating that I had to hang on to the grass for fear of falling into the sky.

Although the swifts were masterful, they had reckoned without my fat, fluffy cat. Bonnie looked as if butter wouldn’t melt, but one day I came into the kitchen without my glasses on, to see something wholly unexpected in her food dish. I squinted, crouched down. There was a live swift, panting.

What to do? I picked it up. Close up a swift is a scimitar of charcoal-brown feathers, a gaping mouth, bottomless black eyes. I turned it over, to see that it has almost no legs, just little feet for hanging on to the nest that they build from mud. No bird spends more of its time in the air than the swift – only the albatross, with its months of oceanic exploration, comes close. Swifts mate on the wing, and even sleep in the air like so many bobbing boats.

I wondered if I could launch the swift again. I took it outside. It was a bright day, and I could hear the other swifts screaming. Would this bird hear them, try to join them? Did I have the guts to just throw it into the air, knowing that if it didn’t fly it would crash to the ground, maybe injure itself even more?

I didn’t have the courage. To this day, I don’t know if that would have been the right thing to do. I put the bird in a box, looked in the phone box, eventually found a bird sanctuary run by a woman in Walthamstow, of all places. Her tone on the phone didn’t give me comfort or hope. She briskly informed that these birds need to eat insects more or less continually, and that they do notoriously badly in captivity. Nonetheless, she was willing to try. For reasons that I can’t now remember, I couldn’t take the bird to her, so I called a taxi, explained my mission, paid him, put an envelope with some money for the sanctuary in with the bird.

The cat rubbed herself around my legs, miaowed.

‘Bugger off’, I said, even as I spooned food into the bowl that had held the swift an hour previously. I understand about the hunting instincts of cats, but it doesn’t mean I have to like it. How we reconcile ourselves to the fact that our beloved cats kill birds and mammals and frogs by the hundreds every year is an individual matter, but I am glad that my current rescue cat shows no inclination to go outside.

I never knew what happened to the swift, beyond the fact of its arriving safely at the sanctuary. Part of me didn’t want to know. If I didn’t know for sure, I could look up at the swifts cutting through the air with fierce wings, and imagine that my swift was one of them, barrel-rolling through an airy sea of pollen grains and parachuting spiders, uttering its battle-cry with berserker delight.

A few years later, I met my husband-to-be, and I sold the house. We were packed up ready to move and all the documents had been signed,  but the company who were supposed to be helping us to move let us down. We were marooned, in a house that was no longer ours, but with no way to move on. The new owners were in the garden, hacking down the shrubs that I’d grown for the birds and the bees to make the space more ‘child-friendly’. I wanted to go, but when we finally found removal men who would come and rescue us, it was 5 p.m. and the move would have to wait till the next day.  The new owners were kind enough to let us stay over for one last night. We sat on their bench, in what was now their garden, amidst the debris of the pyracantha and the buddleia and the cotoneaster, and as evening fell the swifts rolled in, dozens of them, rolling and squealing, so fast and frenzied that they seemed like one continuous stream of swifthood. And so I said goodbye to my house in the company of these sky-cutters, and their bravado lifted my heart until I was ready for my new adventure, too.