A week before Lance Armstrong bids for a seventh Tour win, former England footballer Geoff Thomas started his assault on the 3,484km route.
Thomas is in remission following his bone marrow transplant
In itself, the achievement of completing one of the world's great sporting obstacles would be remarkable enough. But the ex-Crystal Palace midfielder is currently in remission from leukaemia.
The 40-year-old, who has already raised £55,000 for Leukaemia Research ahead of his marathon journey, admitted he was starting his ride "naively".
Thomas, who started his challenge on Saturday a week ahead of the actual Tour, told BBC Sport: "I'm just going to try to enjoy it as much as I can and work hard when need be.
"But to raise the sort of money to say how grateful I am to all the people who helped me, I felt I had to do something extreme. And to complete it would be a major feat."
Thomas was diagnosed with life-threatening chronic myeloid leukaemia in July 2003 and underwent a bone marrow transplant in January 2004.
His ambitious Tour bid, however, becomes more understandable after a friend got him interested in the rigours of cycling's blue-riband event.
"(Six-time Tour winner) Lance Armstrong (himself a cancer survivor) has been a real inspiration," revealed Thomas, who plied his trade as a footballer at a host of clubs, among them Rochdale, Crewe, Nottingham Forest and Wolves.
"The book (Armstrong's autobiography) was sent to me by a friend a couple of weeks after being diagnosed. I was already in a positive frame of mind about how I was going to fight this disease, but the book sealed it.
"What he's gone on to achieve is amazing. He was barely given a chance of surviving let alone going on to win the Tour de France."
Thomas is under no illusions about matching the ease with which Armstrong seems to ascend some of the toughest climbs.
A self-confessed and newly converted "bike nut", his decision to take on some of the toughest mountains in cycling has not met with universal approval.
"My doctor raised eyebrows when I asked if it was possible to do the Tour," he said. "But there is no medical evidence that pushing the body will bring on the disease again.
Thomas will eventually have to climb some of the toughest ascents
"Added to that, there's the missus. I now know not to talk about cycling and a certain hill I may have tackled that day.
"Her eyebrows go up quickly and she turns her back on me. She'll lock the bikes in the garage afterwards! At the moment, they're my pride and joy in the house."
Thomas won nine international caps during Graham Taylor's England reign in the 1990s.
But the high spot of his club career was undoubtedly when he led Palace to the FA Cup final in 1990.
However, he is arguably better known for a diabolical miss while representing England against France, which he now sees as a blessing.
"I'm not, say, an Ian Botham who can raise millions of pounds," he said. "But even my miss against France keeps my name going in the public eye. If I can use that to the good, it's all the best, although I certainly didn't feel good about it at the time!
"The cancer has made me stop moaning about something trivial. It teaches you a lot in life and how to move on to the next day."
Thomas hopes to take his experiences from football to inspire him on some of the Tour's tougher days.
"I think when you've been a professional sportsman, the challenge is the thing you most look forward to," he said. "It's like when we faced Liverpool in the FA Cup semi-final when we'd been beaten 9-0 by them earlier in the season.
"It was a masssive ask that day, as it will be up terrains like the Pyrenees and Alps.
"And if I do this, it will be biggest the achievement of my life. And if I get to the finish on the Champs-Elysees, I will be an emotional mess as it is only two years ago that my life got turned upside down."