The head of the French delegation at ICM in 1950 was Jacques Hadamard, the very prominent French mathematician; he was 84 years old. He had been a refugee in the US during WWII. In the spring of 1950, it appeared that the State Department would not grant him a visa. The reason was that Hadamard was very engaged politically on the left, considered to be close to the Communist Party. The French delegation, including Laurent Schwartz who would receive the Fields medal at the ICM, decided that they would not come if Hadamard did not get his visa. They entrusted their passports to one of them who would give the go ahead only if Hadamard's visa was granted. In th end, Hadamard did get his visa, and the French delegation sailed to Cambridge.