On June 18, 1963, after besting Henry Cooper in a match in London, 21-year-old Cassius Clay turned his attention to Denver-based boxer Sonny Liston — the only thing standing between Clay and the world heavyweight title. “Liston will fall in eight (rounds) to prove that I am great,” Clay told the assembled cameras, having referred to Liston as a “tramp,” a “bum” and an “ugly bear.” Liston responded in kind: “Well, I imagine that if he would come to me, I’d kill him,” he said in a TV interview.