A few months ago at a Pugwash conference in San Diego, I had a long chat with Sergei Kapitsa, the famous son of the much more famous Peter Kapitsa, the Russian Scientist and Nobel Laureate who had worked with Rutherford at Cambridge but was prevented from returning to Cambridge by Stalin. We were speaking of Andrei Sakharov, winner of the Nobel Peace Prize in spite of having designed the Russian H bomb. Sakharov and Peter Kapitsa were close friends and Sergei told me of various meetings in their home in Moscow. While at Russia's 'Los Alamos' (Sarov) Sakharov had constructed the larges bomb ever produced - a 100 megatonne H bomb, equivalent in power to 10,000 Hiroshima bombs. They did succeed in getting it into the air and dropping it but had to restrict its power to 50 megatonnes or it would have blown the aeroplane out of the sky. This was purely a propaganda exercise as the bomb had to be slung beneath a huge slow moving aircraft which could be easily destroyed from the ground. Sergei told me that there was a plan during the height of the Cold War to explode such a weapon just beneath the sea off the coast of Western Europe thereby producing tsunamis and flooding much of the low-lying parts of Western Europe including East Anglia, but in the end in the face of opposition from Sakharov and others, the scheme was not of course put into practice. Sergei told me that an account of this was given in Sakharov's autobiography, which I have but cannot find any references to giant wave production. If any of our colleagues have fuller details of this, I would be most grateful to hear of it. Incidentally, I was talking to one of Sakharov's old colleagues when I visited Sarov some years ago and he told me that he had offered a replica of the 'biggest bomb in the world' to join with the existing 'biggest bell' and 'biggest cannon in' Red Square. His offer was not taken up! Maybe some of this will be helpful.