I forgot to mention: another 40 or so climbers also passed David on the way up. No-one was coming down at that time in the morning. The weather was good, you see.

The amputee, Mark Inglis, had lost his legs to frostbite, being stormbound on a mountain for a time that escapes me. Something like two weeks! He also cycles competitively.
It looks as if he'll lose a finger-joint from this experience. Some people are hard to stop.