The weather in 1976, like the football ten years before, lingers in our national memory. But already on some measures this year is worse. Back then, the heat was drier and the nights cooler. We have already had six days above 35C, for the first time ever, and more warm nights in a single week than in the entirety of 1976. A recent study by British university researchers suggested that during eleven hot days in June, the weather in England and Wales was responsible for 2,200 deaths. Rather than a summer lull, my hospital is dealing with the sort of surge we normally see in winter. The same is true nationwide.

Those of us not hospitalised by the heat will be noticing the sheer quantity of perspiration of which we’re capable. Sweating, like much that makes us human, isn’t unique to us, but it is unmatched – and it is what allowed our other qualities to develop.

Sweating when you have fur is like getting wet while wearing cotton, making for a poor way of controlling your temperature. In extreme conditions, we can sweat litres per hour. We can do that because we’re functionally nude. Quite why we lost our fur is unclear. Perhaps our distant ancestors, as the forests of Africa’s Rift Valley thinned, and they took to the savannah and to their hind legs, only needed fur on those bits of their upright bodies most exposed to the sun – the tops of their heads.

We became naked bipeds well before our brains grew. In the wake of becoming bipedal we became massively better at sweating. Only a million or so years later did natural selection take advantage. Overheating is as much a problem for an organic brain as for a microprocessor. Once we had developed such a power to sweat, our brains could grow – and they did.

In the hot weather, they start to fail. Few of us feel most alert when we’re hot, but the elderly and the frail suffer most. In Latin, to be delirious meant to move out of your furrow: you became delirious when you couldn’t plough straight. Heat will do it to all of us, and it does it to the frail first.

The wards and emergency departments don’t fill up because the NHS is failing, but that certainly makes it worse when they do. Capital budgets have been endlessly raided to meet the front line’s more immediate demands. Over time the effect is that the front line suffers, as the estate falls around it. Our hospital estate is old and crumbling and poorly built. Air conditioning is largely absent, even for those who need it most, and fans are sparse at best, amateurishly plugged in ad hoc rather than being part of the design. Excess deaths are easy to model and hard to properly count. But Brits are built for drizzle, the NHS is built badly even for that, and the summer surge of heat-related ill-health is real.

Look at other countries and the wider lesson is that the dangers aren’t extremes of temperature but a failure to be ready for them. Norway does better in cold winters than we do; Spain better in hot summers. Mortality tracks unpreparedness. Those most worried about global warming should not chiefly be asking us to live a bit less and use less energy. They should be pushing for the buildings and transport and cooling systems that let us live more, and more healthily, whatever the weather.

I saved a man’s life by having spent my boyhood reading James Herriot

Henry James said the two most beautiful words in the English language were ‘summer afternoon’, but they lose their charm on stifling wards or in care homes with windows sealed shut. Our evolutionary triumph leaves us exquisitely vulnerable to heat. As a junior doctor one summer I was referred a farmer with seizures. They’d been brought on by heatstroke, and they weren’t stopping despite the emergency department giving him the right drugs and managing to find not one but three portable fans to plug in next to him.

The muscular activity of the seizures kept his temperature high, making for a vicious circle leading to brain damage and death, one we British doctors aren’t used to seeing. Anaesthetising him was the definitive solution, but I remembered reading about a vet who treated heatstroke in a cow by hosing it down. While waiting for the anaesthetist I covered him in a sheet, soaked it in water, and put ice on top. By the time my colleague from intensive care arrived, the seizures had stopped. I saved a man’s life by having spent my boyhood reading James Herriot.