Hi Simon, I'd be happy to come on this ride, and do any waymarking, TECing, and encouraging as necessary.
With this many riders, and even with a sag wagon to help deal with mechanicals, I suspect there's a chance of multiple punctures, so my deft puncture-repairing-ness could be called upon!
This year I intend to carry at least three inner tubes, plus puncture repair kit and tyre boots, having exhausted my supply of inner tubes on November's ride! (On other people's bikes, not my own).
(Famous last words. I had to repair three punctures on one journey on my own bike last week. I've now put two new tyres on!)