So I have no special knowledge, but I presume a railway timetable, relying as it does on drivers being at a certain place at a certain time to take the next train out, has some resilience.
But if you pass the point of resilience, you get spectacular collapse.
So here's what I think is happening at Cambridge after my observations travelling on Great Northern for the last few weeks. Our semi fasts became Brighton services, which would have been great (especially for me), only they basically don't run.
The semi fasts were the main service from places like Royston, Letchworth, etc. They're also served by the slows, but because of the switch to class 700 for the slow trains a lot of those are getting cancelled too.
Which means the only service left on the GN Cambridge route that was, at least in the first week, still reliable was the express.
But the express has been pressed into service to replace the non-existent Brighton semi fast, which means it gets late.
And the sheer number of cancelled trains (all the semi fasts and quite a lot of the slows) means drivers aren't there to take them out on time, so they get later, so the driver isn't at the other end in time to take the next train out.
So you have trains sitting on platforms waiting drivers who are stuck elsewhere on the system who can't get to their service because the trains are all late or cancelled.
As more trains get late or cancelled, the driver shortage gets worse, which means more trains get late or cancelled. It's a feedback loop, a death spiral, if you will.
The service today was truly dire. Not really worthy of the name. I dread to think what will happen next week, but given the way out of this requires driver training, and you can't train drivers if there are no trains running to train them on, there's no way to interrupt the death spiral.
At some point in the coming weeks, or even days, the service between Cambridge and London on the East Coast Mainline, be it called Great Northern or Thameslink, will simply cease to exist. It's the inexorable result of a service that's entered this "delay/cancel, no drivers, delay/cancel, fewer drivers, delay/cancel, even fewer drivers" feedback loop.
Unless there's something I'm missing or there is some sort of stable floor where the service is so massively reduced that the driver logistics become trivial to manage (say one train every 3 hours or something - you could get them between KGX and CBG by taxi in that time if you needed to).
At least those us who live in Cambridge itself can fall back on Greater Anglia, which is now what I'm resigned to doing after seeing how badly GN deteriorated today. It's the poor sods in the surrounding villages I feel really sorry for.