I ran 24.5km on Saturday morning, but it was hard going - I never got into a good rythym. There are just days when it feels like you've borrowed someone else's legs for the day and they don't quite fit. On those days the last 2km is the worst. At that stage you know you are nearly there, and so you gradually allow yourself to hear all the things your feet and legs are telling you. Suddenly everything seems uphill and upwind.
At brunch later, a friend told me about a technique he uses. He runs for 9 minutes, then walks for 1. He does this right from the start of the race, and claims that it helps him go further, faster, feeling better. To me, the idea of walking feels like cheating, but I'm hoping to grow out of that. It's certainly more culturally acceptable in trail running to walk from time to time, especially since there are hills that you just cannot run up. In marathon running though, it feels like I'm not playing the game. Maybe next time. I assumed it was also for wimps, until I asked him what sort of time he does: under 3h30m. His best time for 21km is 1:25. So maybe there is something in it.