Within a couple more miles it was there again. Like toothache. And as with toothache, there is always a short passage of time when you think you might merely be imagining pain, even inviting it. Which makes you feel either foolish or guilty or both.
Then you move onto the analytical stage. What is pain, after all? It's just nerve-endings, isn't it? Try and think about all the places where you don't hurt. Isolate and ignore the bit that does. Don't even glorify it with the word 'injury' because that's just what it wants to feel big and important. Refuse to think of it as anything more than a minor niggle. There you go. Just relax. Mind over matter.
Then you move onto the realisation that your stupid calf muscle still hurts, in fact hurts more, and that in fact, as when you find yourself driving a car with a bumping burst tyre, you are going to have to make an immediate adjustment and become that most pathetic of creatures, the walking runner. Forget the watch. Forget the marathon - at least the 2013 version.
As the headmaster played by John Cleese in Clockwise - the film made of Michael Frayn's play - memorably exclaims, when yet another twist of fate prevents him from getting to the conference he is due to address: "It's not the despair. It's the hope." Wise words.
Let's try and put a positive spin on this. Although I started training for the London Marathon back in September, at least I've had the benefit of running for seven months, with all the plus points that entails for health. At the point where my leg betrayed me, I felt fit as a butcher's dog.
All right. Let's try again. Although I can't now run the London Marathon, I am performing a statistical service to those who can, because the number of those entering is always several thousand bigger than the number who toe the line, and thus, by taking up one of those non-running places, I am freeing another runner - someone, somewhere - to take part. It's like an endurance running version of the pairing system that operates in the House of Commons, freeing opponents of the obligation to roll up and vote, as they would only cancel each other out. CHEC
All right. Let's try again. At least I now have something in common with Tirunesh Dibaba – she had to pull out too!
All right. Let's try again.
Actually let's not.
Everywhere, it seems, there are earnest figures in dayglo yellow, pattering along the streets, running on the spot as they wait to cross the road, checking their watches as they turn corners. They're all going to be a part of it. They are all going to get swept up in that big wave which will carry 35,000 through the streets of the capital on Sunday, April 21. It was a date that meant excitement, even trepidation. Now - for me - it means frustration, disappointment.
But if I can't be there, I will have to content myself with starting training even earlier for next year's marathon and, on the day, looking out for those runners I know are taking part – injury permitting. I will be looking to see how Michel Roux gets on – weirdly, when I asked him at the London Marathon media lunch about his injury problems he described an intermittent pain in his calf which...but enough of that.
I will also be keen to learn how my friend from Reuters has got on. This is a serious runner who has competed in the last couple of Londons as part of his overall training for Ironman events. (Who knows – I am sure there will be those who take part in Ironman events as part of their overall training for Titaniumman events comprising a swim across the Atlantic, a bike ride across the United States and a concluding run back again.)
The "training" runs have seen him stopping the clock in the 3 hours 20min region. And this year, with no iron or titanium-man commitments, he is taking the marathon seriously.
His preferred method of proceeding over 26 miles and 385 yards is that espoused by the US runner and writer Jeff Galloway which entails interspersing the run with regular walks. Thus, for example, he might run for five minutes, then walk for a minute, then run for five, and so on.
He found this working very well for him in the last two years, as he eventually overtook runners who had passed him earlier in the race and felt that he finished far fresher than the bulk of those around him.
The downside of this approach, of course, is that you can find yourself wanting to extend your walkies if you are not careful and disciplined. The other side effect, he maintains, is felt most obviously in the early stages of the race. As the Ironman slowed into his first scheduled walk he became aware of urgent, well-meaning support from spectators lining the route.
You imagine them going back home and recalling how they saw this one runner struggling before he had even done the first mile: "He'll probably still be out there now...the funny thing was, he looked pretty fit. Still, you can't mess with the marathon, can you?"
Mike Rowbottom, one of Britain's most talented sportswriters, covered the London 2012 Olympics and Paralympics as chief feature writer for insidethegames, having covered the previous five summer Games, and four winter Games, for The Independent. He has worked for the Daily Mail, The Times, The Observer, the Sunday Correspondent and The Guardian. To follow him on Twitter click here.