Sunday morning 9.23am: I am taking a piss in a bush next to a man who is dressed as a Teletubby. Po, possibly. Behind me, an Archbishop is flat on his back undertaking a complicated and dangerous-looking manoeuvre with his legs crossed at an improbable angle. There is a strong smell of liniment in the air.

But no, it's not the aftermath of one of Jez Brown's parties. I'm in Greenwich Park and in 22 minutes time I'm supposed to be starting a run even longer than one of those Hatton gallops from his own penalty box into the unknown territories of the opposition half.

In less than four hours time, I hope, I'll be surging gazelle-like along The Mall, the good natured crowd, as one, chanting my name. Halle Gabriellesellasi gasping helplessly in my wake. David Coleman exploding with excitement as he searches for the words to describe this historic event. That famous theme music playing.

9.24am: My reverie is broken by the sound of Po's mobile phone ringing to the tune of that famous theme music. I dodge to avoid his stream as he reaches into his costume to find it. This would be a bad time to pull something. I wait to hear whether he answers "Eh Oh". "Alright Dave," he says, disappointingly.

9.43am: Am lined up with another 20,000 bodies at the Mass Start. All of them are clearly fine athletes. Perfectly honed. Well prepared. Quick. Particularly that 84-year-old woman to my left. Why didn't I train more? Perhaps it's not too late to feign injury.

9.44am: A minute's silence for the Queen Mother. Gawd bless 'er.

9.45am: Showtime. The gun goes. People cheer. Nothing much happens.

9.46am: A slow kind of shuffling starts. Approximately the speed of a Mark Abbott sprint. This would be a comfortable pace. I fear things might get faster.

9.48am: Things get faster. Bugger.

9.52am: We cross the line. Thanks to cunning technology, the small plastic microchip threaded through my laces will trigger as I go across the scanner to give me my official time. Let's hope there's been no Logica involvement in the system.

10.31am: Mile 1. A whole one-twenty-sixth of the distance is in the bag. This is not a comforting thought. Crowds shout encouragement. Bands play. There is a carnival atmosphere. Small endearing children hold their hands up for high fives. Delightful youngsters.

11.15am: Mile 11. Have been running non-stop for 90 minutes. Er, just like a usual Sunday morning on the football pitch. Normally that would mean heading off to the pub. Instead there is still the small matter of 16 miles to run. Doh.

12.10am: Mile 17. Now entering totally unknown territory. Feel OK. No sign yet of The Wall, which experts say will be hit sometime in the next four miles. Maybe the experts are wrong.

12.48pm: Mile 21. The experts are not wrong. "There is no wall," a man behind me keeps shouting. He is a fool and a liar. It's real all right, and I've hit it just as certainly as the ball from a Craig Taylor free kick.

1.22pm: Mile 24. Crowds shout encouragement. Bands play. There is a carnival atmosphere. Unfortunately I am in too much pain to notice. My legs feel like they've been clattered repeatedly by Trovato tackles for four hours solid. Small annoying children hold their hands up for high fives. Out of the way, little brats.

1.31pm: Mile 25. Am still not sure whether to believe I will finish. Am sustained by the knowledge that as long is I don't stop running, I'll be inside 4 hours and it will cost Sidaway money.

1.42pm: Mile 26. Into St James's Park. Four hours looks to be in the bag, but an annoyingly old-looking woman surges past me to take the gloss off things. Am vaguely aware I should be enjoying this bit but legs/joints/feet are far too painful for that. Cross the line, remembering a suitable gesture to the camera for the 4-hour doubters.

1.44pm: Have been standing, gasping and grimacing for two minutes just the other side of the line .The time for elation, joy, relief, pride will come later. Quite a bit later. For now, I'll just be happy to work out how to walk the 30 yards to the bloke giving out the medals...