The cargo they will collect is a consignment of mixed plutonium and uranium oxides -- Mox for short -- which was delivered by British Nuclear Fuels Ltd to Japan, where it was to have been used as reactor fuel. The Japanese discovered that BNFL had falsified its records, and demanded that the company retrieve it.

BNFL, which is a state-owned company, must comply if it is not to lose future markets for its Mox fuel. It must defend those markets in order to justify the government's decision in October to allow the Mox plant at Sellafield in Cumbria to open. The Mox plant opened in order to make sense of the reprocessing operations at Sellafield, which extract plutonium and uranium from nuclear waste. The reprocessing was permitted in order to provide a reason for Sellafield's continued existence. Sellafield exists in order to keep the British nuclear power programme running. The British nuclear power programme exists because ... well, it exists because it exists. There may once have been a reason, but if so it has been lost in the mists of time.

Britain's nuclear policy, in other words, is like the old woman who swallowed a fly. Every solution is worse than the problem it was supposed to address. Every new justification ratchets up the probability of a major nuclear accident or breach of security. Yet the programme's institutional momentum carries all before it.