London Marathon: 100 Marathons in 100 Days by Hannah Cox

“Everyone tried to shut me up at first — people didn’t believe I’d actually do it,” Cox says.

But on October 26 last year, he traveled from the Attari-Wagha border between Pakistan and India to Kolkata, just a few miles from where his father, Derrick, was born.

He was true to the route, which meant sometimes there were days when he ran 42km along a highway “that was boring as hell” but other days were in nature reserves, along canals and through farmers’ fields.

There were cows, snakes and goats on the roads, while drivers regularly traveled on the wrong side of the highway. Some roads were busy and he has a scar on his right leg from a collision with a motorbike while he was running.

He even required a police escort at times as he passed through areas known for regular deadly tiger attacks.

It was often hot, dusty and smoky, and although she had spent two weeks doing sessions in a heat chamber, it was nothing like her experience.

And then there was illness, which played a big role in her losing more than 10kg during the challenge.

One such episode coincides with an encounter with a more surreal opportunity.

“It was the 24th and we met Richard Branson at the Taj Mahal,” she says.

“He was there to organize a charity cycling event and we were walking around the Taj and I was feeling worse and worse.

“Earlier in the evening, he invited me to dinner at a really expensive hotel. I snorted an Old Fashioned cocktail and I was like: “Oh my God, I’m going to be sick”.

“I had to run to these really fancy toilets and I was sick all over.

“The next day, I had to run a marathon and five people who were part of Richard Branson’s charity event decided they were going to run with me. I was sick on the side of the road all day but I just knew I had to finish.”