The seeds for Thompson's mission impossible were sown three years ago when he completed the Amsterdam marathon in a stupendously quick time of 2-25. Rather than feeling a sense of elation, Thompson suffered an existential crisis and decided that he would no longer obsess about speed. Instead he wanted to rediscover his love of running and its ability to help him switch off from the outside world.
"I struggled with my mental health after Amsterdam and really didn't have a great six months," he said. "The relationship I was in ended and I decided I didn't want to run any more because I blamed it for that break-up and losing contact with friends.
"But I realised after four or five months that I needed to run. It wasn't about running quickly any more but having something to turn to to get away from things. Doing these challenges gives me focus and, just as importantly, helps me raise money for charities I care about and people close to me."
After rediscovering his love for running with the 44-marathon challenge last year, Thompson began his Tour de France attempt on May 19. Over the course of 10 weeks he has grappled with blazing 35C heat and grass verges where one false step could mean a fatal fall off the side of a mountain.
There were moments when he felt he could not go on but the incentive of "breathtakingly beautiful" mountain views always kept him going.
At the finish line, Thompson felt "huge excitement and pride" but was too exhausted to have a big celebration, only managing a couple of beers with his girlfriend before conking out at 10pm. To compensate he is planning a party at the weekend with friends and family.
He will then go back to work in a few weeks, before inevitably thinking about his next adventure. Thompson insists, though, that his only focus for now is enjoying the moment.
"I don't know what's next. It's about finishing this and enjoying this. I'm very conscious of not diving into something else straight away. That was my problem last time, constantly thinking about the next thing and improving. The next thing will just be whatever comes along."
