http://hn.vernccvbvyi5qhfzyqengccj7lkove6bjot2xhh5kajhwvidqafczrad.onion/stories/38519877
The Butex process ran at sellafield from 1951 to 1964, only the period of 1951 to 1958 was producing material for the UK nuclear weapons program, after the successful hydrogen bomb tests the UK signed an agreement to a) use US nuclear warheads in UK bombs/missiles, and b) provide the US with plutonium from sellfield in return.