Michael Johnson won four Olympic titles and eight World Championship gold medals in his career.
But, as world champion, he failed to qualify for the 200m final at the Barcelona Olympics.
He used that as motivation to win gold in Atlanta in 1996, winning both the 200m and 400m titles.
Three years later, at the World Championships in Seville, he broke the 400m world record, running 43.18 seconds wearing specially commissioned golden shoes.
Watch Michael Johnson present the documentary 'From London 2012 to London 2017' on BBC World News at 04:30 GMT on Saturday, 5 August and 10:30 GMT on Sunday, 6 August.