I went flying last week from sherburn, In the morning one of the girls in our office had said there was a no fly zone over leeds, following the london bombings, I checked the notams and found nothing.
When I got to sherburn 1 hour later there was a sign on the door warning of the no fly zone.
If I had been flying from a private strip I would not have known and could have flown right through it, not sure of the results of that!
so even an hour can make all the difference, although I suspect some kind ATC may have put me wise, but not everyone has radio.