Ak Hafiy Tajuddin Rositi was the oldest athlete to compete for Brunei at the London Games at age 21. He had not participated in any previous Olympic Games. Rositi qualified for the Games via a wildcard because his fastest time of 49.81 seconds, set in the 2011 Asian Athletics Championships Men's 400 metres, was 4.11 seconds slower than the "B" qualifying standard for the men's 400 metres. He was drawn in the event's third heat on 4 August, finishing eighth (and last) out of all participants, with a time of 48.67 seconds. Overall Rositi finished 45th out of 47 runners, and was unable to advance into the semi-finals because he was 3.67 seconds slower than the slowest athlete in his heat who made the later stages.