Recognising this ability, in 1965 Caltech asked him to rewrite the undergraduate physics course. The resulting Feynman Lectures on Physics took him three years to create and the accompanying textbooks still represent the last word on the history of physics. The lectures themselves were brimming with inspiring “showbiz demonstrations” as his friend Richard Davies describes them. Most memorably, Feynman used to set up a heavy brass ball on a pendulum, send it swinging across the room, and then wait for it to swing back towards him. Students would gasp as it rushed towards his face, but Feynman would stand stock still, knowing it would stop just in front of his nose. Keen to capitalise on these talents for engaging an audience, Christopher Sykes made his film for Horizon. “He took enormous pleasure in exploring life and everything it had to offer,” remembers Sykes. “More than that, he took tremendous pleasure in telling you about it.”