Unless it somehow managed to burrow a very long way down before exploding, such a weapon detonated beneath the earth's surface would throw up huge amounts of radioactive debris, a danger to all.
David Cameron told the BBC that the UK's huge public deficit was "a clear and present danger" and being honest about the cuts needed to tackle it was the only option.
Refrigerated stores at Nairobi airport and on farms are now completely full, and a huge amount of fresh flowers and vegetables destined for the European market is in danger of perishing, the BBC's East Africa correspondent, Will Ross, reports.
Many companies are spending huge sums of money to protect their employees from viruses, spyware and spam but they could be ignoring another danger, warns a survey from PointSec.