By the age of 21, he represented England in the 1966 Commonwealth Games.
In 1967, he won his first title as British National Sprint Champion.
Barnett, now based in Shoreham, Kent, said as his career progressed the pressure of track racing began to overwhelm him.
“I was flying,” he said. “But in all honesty, my mind had gone a bit.”
In 1968 he travelled to Mexico for the Olympic Games, where he fell into a deep depression.
“Nowadays they have psychiatrists, but I had always been on my own,” Barnett said.
When it came to the deciding race, he lost out on the chance for a medal.