Clue 1: I am a doctor. I was born in Harrow, England, in 1929.
Clue 2: I am the first person to run a mile in less than 4 minutes. On May 6, 1954, I set a world record of 3 minutes and 59.4 seconds.
Clue 3: I retired from racing in December 1954 to practice medicine. I was knighted in 1975.
Who am I?