Today, five endurance cyclists will begin an epic battle to become the fastest person to cycle around the world. They could notch up an average of up to 225 miles a day.
At 12 noon GMT today the riders will set off from the Royal Observatory in Greenwich for the 18,000 World Cycle Race.
One of the top contenders, Lee Fancourt, believes he can complete the challenge by riding approximately 225 miles (362km) a day for 80 days. Some days he will clock up to 250 miles a day. Including air travel the whole circumnavigation should take under 90 days, which will smash the Guinness World Record of 106 days, 10hrs and 33mins, set by Alan Bate in 2010.
"If my bones, my tendons, my ligaments and my muscles can stay in one piece, I will be back in under 90 days," the 37-year-old from Gloucester in the UK told BikeRadar. He has been putting in huge miles recently and rode to southern Spain and back in January.
His route, programmed into a Garmin, will take him through Europe and Russia before tackling India, the Far East and then Australia and New Zealand.
After cracking the Antipodes, North America needs to be conquered before the final gruelling leg from Portugal back to London. He will ride more than 18,000 miles.
Fancourt will be supported on some legs, notably India and America by family, but will be battling alone for much of it, sleeping rough most of the nights away from his two children.
"I enjoy cycling so much and other than being around my own two kids, the time I'm at my most happy is when I'm riding. I think this is why I can keep going and going and going and not get annoyed," he said.
"I want to break the world record so I want to do it as fast as possible," he said. I don't want to use thick tyres, I want to do it fast. Obviously in places like India I'll do it on 25mm but I'm just heading for speed."
Other riders include Breifne Earley, Prasad Erande, Jason Saunders and the only woman taking part, Fran Hollander.
Follow the second Brooks-supported World Cycle Race via the website. Lasts year's inaugural event was won by Mike Hall.