I was wrong. There are any number of London marathon training blogs.
My first strategy was flawed, relying on a Technorati watchlist. The watchlist strategy is: "London marathon" training OR http://www.london-marathon.co.uk/ but this found very few.
I have now discovered two much more fruitful resources:
The rather oddly named Running Blog Family
The Runners World forum for London marathon bloggers.
There are some listed that are no longer maintained, but that's the way of the world.
