He had become involved with the military just before the war in the Thetis disaster. Does that ring a bell with you, Martin? No. That was a British Navy Submarine which sank in quite shallow water, but the crew, I think maybe one or two people escaped, but they were nearly all drowned, or killed by respiratory diseases. So Jack had- in his life, he had done many things but included a bout of respiratory physiology with his father, John Haldane, J. S. Haldane. And so he became, particularly after the Thetis disaster, when he was doing things for- both for the Navy and for C. B. Gorman, who was a company which built diving apparatus and diving locks, testing it out. And, there's somewhere in the library here, there's a graph published from that work of time to convulsions against oxygen pressure or CO2 pressure, but that kind of work. He loved doing experiments on himself. He was very proud of it. He was particularly proud of having badly damaged his coccyx from bends, from nitrogen bubbles, or so he said. So, wherever he went around, he had this inflatable cushion which he sat down, and it made quite noise as he sat down on it. And everybody was very entertained by that.