UK
It was scheduled - albeit with around 30 minutes notice - but it was scheduled for 21:30. When it didn't happen as scheduled they just had to be ready to go to it when it started.
The PM's statement 30 minutes ago. Seemingly unscheduled as the news channels weren't trailing it, the PM making a live statement announcing that another attack may be imminent, just compounding the day's events.
It was scheduled - albeit with around 30 minutes notice - but it was scheduled for 21:30. When it didn't happen as scheduled they just had to be ready to go to it when it started.