Everybody back on the coach

"Thirteen of fourteen" is useless on a riverbank. Every result is a list of people, and any total is derived from the list rather than the other way round — because the two seconds before a coach pulls out are not enough time to work out who is missing from a number.

A guide who got halfway down the list before somebody shouted has not established that the rest are missing. Unreached people are their own bucket, and a roll call that has not reached everybody clears nobody. A green tick appearing mid-count is the failure that leaves somebody behind.

Four out and four back can mean three of the same people and one stranger. Roll calls are compared by person, so somebody still at the lookout point shows up even when the count matches — which is the entire reason to run a second one.

Stadium doors are deliberately online-only, because two phones showing one screenshot must not both get in and only a server can arbitrate that. A roll call has nothing to arbitrate: twenty-five known people, one device, a guide who can see them. It works with no signal and syncs afterwards, and the gap between when it was taken and when it arrived is kept — because after an incident somebody will ask.