Back in the late 1970s, with the Cold War at its height, we schoolboys used to ponder, with grim fascination, what would happen if the balloon went up. A teacher had got hold of a copy of the recently unbanned BBC documentary The War Game, a dramatisation of a nuclear strike on southern England, and it scared the heebie-jeebies out of all of us. Two decades later a different grim fascination infected the world: the Millennium Bug, the computer meltdown that was supposed to accompany the last second of 1999.

Take one real threat, one imaginary and then add 20 years of growing anxiety that humankind may be altering the climate to disastrous effect, and the result is the idea that humanity, or at least our civilisation, is doomed in quite short order.

This thesis has become strangely fashionable; indeed, to argue against it one feels like a flat-earther. Sometimes threats are real and truly existential - such as global nuclear war. Sometimes they are fanciful, such as the Millennium Bug. And sometimes they lie somewhere in between, such as climate change. But surely we can all agree that if not humanity then certainly our current civilisation is in its final days?

Well, maybe. But what if it isn't? This was the possibility I wanted to explore in my new book. What if, far from being about to end, not only our planet but we ourselves and even something resembling our culture were to rumble on not only for a few more decades but for centuries, or even millennia? It is a heretical thought, perhaps, but what if, just maybe, some aspect of today were to survive to the end of time itself?