I don't even know his last name, and he doesn't know mine. But he's called Josh, he's a transportation engineer from Boise, Idaho, and he made a small difference to several people's lives today, mine included.

I've run over twenty marathons, but when I did the New Orleans Mardi Gras marathon today, I decided to do something I'd never done before. I ran with a pace group led by Josh, who had sufficient confidence in his ability to finish the race in 3 hours 50 minutes, at an average of 8 minutes 49 seconds a mile, that he was willing to run all 26 miles holding a placard announcing this fact and invite others to follow him.

For the first 19 miles or so, I stuck close to him, setting probably the most consistent pace of my running career. Sometimes I found myself looking back and slowing to keep him in sight, which went completely against the grain, though I knew it was common sense.

Then came the only hill on the course - a very modest bridge - and I began to slip behind Josh as he kept up the same unrelenting cadence. He disappeared into the distance, and I never saw him again.

After that I hit the wall, and finished the course with a combination of walking and running. At one stage, one of my fellow runners came to a halt in front of me, turned round, looked me in the eye and said: "Come on Phil." My name was written on my back. "What's with the walking? You can do better than this." I grinned, resumed my slow trot and finished in 4 hours 13 minutes, coming 623rd out of 7,400.

It would have been a lot slower if it hadn't been for Josh and the other unnamed competitor; people like them are one of the reasons I run. I do it partly for the sense of achievement and the high as I cross the finishing line, but part of it is just for the sense of we're all in this together, we've got to look after each other. A bit like life, really.