He made global headlines in 1976 when he revealed a major scandal at the Olympic Games in Montreal. 

Fox was competing in the fencing round when he came up against Boris Onishchenko, a soldier in the Soviet Union Red Army.

As they fought, a light came on prematurely to indicate a hit for Onishchenko.

"All I could think about was that Onishchenko had a weapon that was not properly working, and then over a period of minutes, because he was going to put it back in his bag and because of the way he he wanted to put it back in his bag, I felt there was something dramatically wrong." Fox told the BBC  later.

The truth soon came to light.

"The weapon had definitely been tampered with. Someone had wired it in such a way that it would score a winning hit without making contact." Montreal 1976 official Carl Schwende revealed.

Onishenko was disqualified from the event after the mechanism was discovered.

Fox and his British team mates Danny Nightingale and Adrian Parker went on to win the gold medal in the team event after a particularly impressive performance in the run which concluded the competition.

Fox woke his commanding officer in the middle of the night to impart the news of his success and carried the British flag at the Closing Ceremony.

When he returned home, his army colleagues hauled his Land Rover through the streets in a victory parade to celebrate the gold medal.

Janusz Peciak of Poland, the individual gold medallist at Montreal 1976, recalled Fox's actions.

"I always say that Scotland Yard is the best in the world for investigation, but Jimmy Fox really helped me to win the medal, because if Jimmy had not caught him, Onishchenko would have got away with this and would have won the gold medal instead of me." Peciak said later.

An army sergeant in the Royal Electrical and Mechanical Engineers (REME), Fox was the outstanding competitor at national level for over a decade and competed in four Olympic Games finally fulfilling his ambition with a gold medal in the team event at Montreal 1976.

He was always known as "Jim" but he was actually born in Pewsey Wiltshire, as Jeremy Robert Fox. 

Fox first competed in the Olympic Games at Tokyo 1964, finishing 29th.

He improved to eighth at Mexico City 1968. 

Fox was dissuaded from retiring from the sport by coach Ron Bright and finished fourth at Munich 1972 before his Olympic triumph in Montreal four years later.

Fox was promoted to captain after his success and later became chairman of Pentathlon GB.

He was also decorated with the Order of the British Empire for his services to the sport and later recognised by the REME with a Corps Lifetime Achievement award.

He was awarded the Olympic Order in silver in 1998.

In 2016, Fox was invited to open a gymnasium at the army barracks in Lyneham in Wiltshire which had been named in his honour.

He suffered from a degenerative disease in the later part of his life but is understood to have died peacefully yesterday.