Doris Lessing provides a lovely description of this in the first volume of her autobiography, Under My Skin. “Once I was making a mental list of all the places I had lived in, having moved about so much, and soon concluded that the common sense or factual approach leads to nothing but error,” she writes. “You may live in a place for months, even years, and it does not touch you, but a weekend or a night in another, and you feel as if your whole being has been sprayed with the equivalent of a cosmic wind.”

Whenever I’ve completed a book, I’ve felt an urge to take a trip. It’s seldom the idea of writing a travel book that drives me, though a book is the inevitable result of a long journey, since I need to pay my way. Necessary episodes of travel constitute my mode of being, and they have intensified as I’ve grown older. I never examined this necessity. I rationalised my disappearing act by talking about growing up in a big family, my hatred of confinement and scrutiny, my need for space, my curiosity.

I always knew travel to be an enhancement of life, something richer than anything I’d experience at home. But then I saw that travel also offers an expansion of time Paul Theroux

That was true, but I had deeper reasons, which I did not fully understand back then. But ageing is the great clarifier, offering unanticipated insights, because ageing is an odyssey of enlightenment and a lesson in timekeeping: you value time as precious and want more. I began to understand that the natural wish in old age for more time can be granted by travel.

I always knew travel to be an enhancement of life, something richer than anything I’d experience at home. But then I saw that travel also offers an expansion of time. The German philosopher Arthur Schopenhauer once observed, in a mathematical way, “When we are travelling: one month away seems longer to us than four at home.”