At a Games where the German leader Adolf Hitler sought to promote his ideas of Aryan supremacy Long confounded his ideology by establishing what would turn out to be a lifelong friendship with the black American who finished the Games with four golds.

Long and Owens exchanged letters until shortly before the German was killed aged 30 in 1943 during the Allied invasion of Sicily.

In his final letter, Long - anticipating his death - wrote: "Go to Germany when this war is done, someday find my Karl, and tell him about his father.

"Tell him, Jesse, what times were like when we were not separated by war. I am saying - tell him how things can be between men on this earth."

Owens, who died in 1980, often recounted how, in the qualifying competition, he was advised by Long to move his starting marker backwards after fouling on the first two of his three allocated attempts.

The world record holder progressed with ease and went on to contest the gold in stirring fashion with Long, who equalled his first Olympic record of 7.87 metres but was to match his concluding effort of 8.06m.  

Owens, who also won gold in the 100 metres, 200m and 4x100m, later admitted that the discussion with Long over qualifying had not taken place, but what was undeniable was how well the two men got on in the wake of their competition - when they embraced under the gaze of Der Fuhrer before posing for pictures while circling the stadium together - and subsequently.

Now Long’s family are putting his silver medal up for auction, with the heirloom set to fetch up to $1 million under the hammer.

Austin Widger from SCP Auctions, which is handling the sale, said: "Luz Long's silver medal from the 1936 Berlin Olympics is highly historic in what it represents."

He added that the historic interaction between the two rivals "showed how sport transcends discrimination and nationalistic divides, and has the power to unite people from the most diverse backgrounds."

Reflecting on those Games, Owens said: "It took a lot of courage for him to befriend me.

"You can melt down all the medals and cups I have and they wouldn't be a plating on the 24-karat friendship I felt for Luz Long at that moment.

"Hitler must have gone crazy watching us embrace."

Albert Speer, Hitler's close ally, did confirm that Hitler was "highly annoyed" by the success of black Americans at the 1936 Olympics.

The two families met up at the 2009 World Athletics Championships in Berlin.

Long's daughter-in-law, Ragna Long, and his granddaughter, Julia Kellner Long, made the decision to sell the heirloom after Karl - Julia's father - died aged 80.

"They consigned the silver medal, and several dozen other Long family heirlooms, to this special auction that is spotlighting Luz's collection," Widger added.