In message , Clive D. W. Feather
writes
Otherwise all those points are set to "needed" (causing them to move if
they're currently wrong). One the train passes over each set they move
back to "free" (unless another route is also holding them)
What's the chances that the points freed at Poters Bar, whist the train
was going over them, allowing the first part of the train in the right
direct and the second part by the point being able to move?
--
Clive.