British distance runner, David Bedford was known for his extreme training volume and famously claimed to have done 50 x 1 mile repeats in a single workout during his peak in the 1970s. That story has circulated among running enthusiasts as a testament to his legendary endurance and grit. He specialized in longer distances like the 10,000 meters and held the world record in that event for a time.
I think he was quoted in Runner's World as saying "It took all bloody day." I would be interested in reading about guys like Mr. Bedford who is still alive! I have asked several marathon questions on LRC and got nothing. I guess there are too many secrets.