"The one dropped on Hiroshima measured 15 kilotons; it destroyed everything within 200 yards and burned everybody within 2km. The warhead carried by a Trident missile delivers a reported 455 kilotons of explosive power. Drop one on Bristol and the fireball is 1km wide; third-degree burns affect everybody from Portishead to Keynesham, and everything in a line from the Bristol Channel to the Wash is contaminated with radiation. In this scenario, 169,000 people die immediately and 180,000 need emergency treatment. Given that there are only 101,000 beds in the entire English NHS, you can begin to imagine the apocalyptic scenes for those who survive. (You can model your own scenario here.)
But a Trident missile carries up to eight of these warheads, and military planners might drop them in a pattern around one target, creating a firestorm along the lines that conventional Allied bombing created in Hamburg and Tokyo during the second world war.
I don’t wish to alarm you, but right now the majority of the world’s nuclear warheads are in the hands of men for whom the idea of using them is becoming thinkable."