It is a truth universally acknowledged that a man approaching sixty must be in want of a walk.

Not a brisk constitutional through verdant countryside, mind you, but a bleary-eyed shuffle around suburban pavements before the rest of the world has even located their slippers. The sort of walk where your only companions are joggers who look like they were genetically engineered in a lab and dog walkers whose pets seem disturbingly more alert than you are.

I recently turned sixty. A milestone, apparently. I celebrated it by forgetting what I walked into the kitchen for and buying a blood pressure monitor that speaks to me in a voice suspiciously similar to a robot. It tells me I’m “borderline,” which I think refers to my temperament more than my systolic reading.

In a fit of health-conscious lunacy, I resolved to take morning walks. You know the type: sensible shoes, fleece with too many pockets, that odd, determined gait that says “I’ve read about this in Reader’s Digest.” The trouble is, I never sleep. I don’t mean the elegant, tortured insomnia of a romantic poet. I mean the kind of disjointed, twitchy half-sleep that feels like someone’s repeatedly nudging you with a stick just as you’re nodding off. I lie there, staring at the ceiling, listening to the central heating pipes make noises like a depressed walrus trying to play the trombone.

So, when I rise at 5:00 a.m. (or more accurately, when I give up lying down at 5:00 a.m.), I resemble not so much a man embracing vitality as a recently reanimated corpse wondering where it left its legs.

Out I go into the damp grey world, breathing deeply of the bracing morning air, which smells faintly of fox piss and regret. The joggers pass me, shiny and smug, barely breaking a sweat. One of them – twenty if he’s a day – calls out, “Keep going, mate! Age is just a number!” I briefly consider putting a foot out to trip him up so he fell into a hedgerow but decide against it on account of the paperwork.

The walk itself is a procession of small indignities: bin men eyeing me with suspicion, as though I’ve escaped from a care home; a yappy dog attempting to savage my ankle; and a neighbour who cheerily says, “Nice to see you out and about again,” as though I’ve just been released on parole.

By the time I return home, I feel marginally better, if only because the ordeal is over. I make a cup of coffee and stare out the window, convincing myself that this is all doing me good. I have a vague, possibly hallucinatory vision of myself at seventy-five, bounding up hills and shouting things like “I’ve never felt better!”

In the meantime, I shall continue my early morning meanderings, fuelled by stubbornness, black coffee, and a vague desire to outlive several people from the local area. If nothing else, walking gives me time to think — mostly about biscuits and the absurdity of modern trainers. And sleep? Well, there’s always the afterlife. Or Radio 4’s Shipping Forecast.