And, welcome to the UK! We only had about three or four minutes warning time available, so when the sirens went off, that was all the time the population had to prepare/shelter, and obviously the authorities also only had that amount of time to decide on a response... This includes getting all your bomber aeroplanes started up, launched and in the air sufficiently far from the airfield to escape the blast radius of the weapons (probably Megaton range) used to destroy it!