An ethereally beautiful winter’s day. I’m staring through the window at the soupy sunshine and the blurred pillars of dense, freezing mist, pondering all manner of significant thoughts. It’s here. The one. The coldest day of the winter so far, and the one I’ve been waiting for.

Stepping outside at lunchtime is painful. I wear a tracksuit top but my legs are bare and stiff and white like a corpse. Yes it’s cold, but it will soon be properly cold, and I need to leave myself a bit of unclimbed track on the garb mountain.

What’s this all about? It’s mid-winter, and here I am, wandering half naked up a main road somewhere in South Gloucestershire, trying to coax some circulation into my lower extremities. The left knee is whining at me again like a lame dog. Motorists gaze blankly at me as they glide past through the patchy fog. Not difficult to imagine their thoughts.

Still walking, still trying to crank up the heart-rate before starting to run, I turn off the main road and find myself on a small country lane. I was here on Saturday, and ear-marked it as suitably off-the-beaten track – even scenic in parts. To my clouded urban eyes, these Cotswold lanes are everything the English countryside is supposed to be.

With a heavy sigh, my hood still up to avoid frostbitten ears, I finally start to run. As the heavy panting starts I look up, and there, a few yards away, is a teenage girl in school uniform, cowering in a hedge, staring fearfully.

I can hear the pain crackle my ankles as I totter past, like Humpty Dumpty on stilts. The icy tarmac road is iron-hard, jarring my knees and hammering my legs into my pelvis.

There’s a giggle behind me. As a few pin-pricks of sweat pop through the pores in my neck and catch the bitter breeze, I begin to feel intolerably miserable, and foolish. And old.

What is it that brings an educated and reasonably rational adult man to this level of desperation and public humiliation?

Well. There are two answers to this question. The complicated one can wait. The simple one can be found inside a shrink-wrapped, clear-plastic A4 envelope that hit my doormat a few days ago. I’d almost thrown it away without a second glance, thinking it was yet another lame attempt to sell me something useless. Then I realised. Against the odds (the chances of gaining a place through the ballot are said to be around 1 in 6), I find that it’s a letter confirming that I’ve been accepted for the 2002 London Marathon. Oh… I see.

I’m warming up. The physiological, biomechanical magic has begun. It’s always the same. Like starting out on a long hike. The first mile is so miserable. My rucksack is too heavy and awkwardly-shaped and my boots don’t feel right and everything is damp and hostile and itchy. But a mile further on it all starts to fit together. It starts to feel right. Five minutes later, I know it’s going to be OK. I yank my hood down. My ears are now throbbing with heat.

The rustic track eventually turns into a larger lane. Now there is the occasional car to add some excitement, but still narrow enough to have to stand still and even sink into the hedge a little way, just to make sure I don’t get jabbed by a wing mirror. Interrupts the rhythm, but preferable to death.

Past the forge and round another corner, where a Union Jack flaps about atop a flagpole in a front garden. This is a curious sight. Bizarre though it might sound to foreigners, we are not encouraged to display the British flag in Britain. Doing so will lead to accusations of belonging to some outlawed far-right organisation. Things like this used to depress me, but not any more. I laugh out loud, and carry on running, happy at last.