In reply to andymac:
Between 1969 and 1971 I worked for the British Non-Ferrous Metals Research Association (BNF) in London. Also working there was a secretary called Melita Norwood, who retired in 1972. Only many years later was she revealed, in her eighties, to have been a long-serving KGB agent. There was much sniggering incredulity among the humanities-trained media types over this "grannie spy" and the rather obscure and humdrum-sounding place where she worked.
Actually she was one of the most important agents ever to operate here. The fissile components of nuclear weapons (uranium, plutonium, palladium, beryllium etc.) are, of course, all non-ferrous metals, and in order to make a bomb these have to be cast and accurately machined into complex shapes, requiring detailed knowledge of their physical and chemical properties. This research was done in the post-war years at BNF, which had some of the best metallurgists in the country. The resulting information passed across her desk, and thence to the Soviet Union where it greatly assisted their atom-bomb project.
She retained her devotion to communism to the end, saying "I did what I did, not for money, but to help prevent the defeat of a new system which had, at great cost,given ordinary people food and fares which they could afford, a good education and a health service".