Nairobi, April 29 -- On May 6 1954, Sir Roger Bannister did what was deemed impossible in athletics: he ran a mile in less than four minutes.

The milestone was celebrated worldwide, not just by athletics fans. It was considered at the time to be a similar achievement to scaling Mount Everest for the first time, which Sir Edmund Hilary and Tenzing Norgay had done the year before.

On Sunday, Kenya's Sabastian Sawe and Ethiopia's Yomif Kejelcha achieved a breakthrough comparable to Bannister's some 72 years ago: running the 42 kilometres of a marathon in less than two hours.

Let's break down this new benchmark and work out how these athletes were able to do it.

What happened in London?

Sawe smashed the men's wor...