During the final training sessions in Tokyo, Talbot organised time trials for the Australians, which were held in front of opposition swimmers in an attempt to intimidate them. O'Brien posted a time of 2 min 33 s, which Talbot felt had a negative psychological effect on O'Brien's opponents. When competition started, O'Brien swam an Olympic record to win the first heat by 2.0 s. He posted a time of 2 min 31.4 s, reducing the previous Olympic mark by 5.8 s, an indication of how much the world record had fallen in the preceding four years. However, in the next heat, Egon Henninger of Germany immediately lowered the mark, and by the end of the heats, O'Brien was the fourth fastest qualifier for the semifinals, with both Prokopenko and Jastremski posting faster times. O'Brien lowered Henninger's Olympic record by winning the second semifinal in a time of 2 min 28.7 s, after Jastremski had won the first semifinal in a time that was 3.4 s slower than O'Brien. This made O'Brien the fastest qualifier for the final, with a time that was 1.0 s faster than the next qualifier Prokopenko, who came second to him in the second semifinal. O'Brien planned to swim the race at an even pace and record even splits for the first and second half of the race. He was mindful of not chasing Jastremski, who was known for an aggressive opening style, which resulted in a faster first half.