Walker broke the World Record in the mile run with a time of 3:49.4 minutes set at Göteborg, Sweden, on 12 August 1975, bettering the previous time of 3:51.0 set earlier that year by Filbert Bayi. It was the first time that the three minutes and 50 seconds time had been broken, and it was a full 10 seconds faster than Roger Bannister's historic sub-Four-Minute Mile of 3:59.4 that was run twenty-one years previously. He was named Athlete of the Year by "Track and Field News" the same year. In the 1976 New Year Honours, Walker was appointed an Officer of the Order of the British Empire, for services to athletics, especially as the first person to run the mile in less than 3 minutes 50 seconds.