At 6:30 this morning, Dominic Irvine and Charlie Mitchell left Land's End in an attempt to break the men's tandem record for cycling between the two furthest points on the British mainland.
The existing record, held by Pete Swinden and John Withers, stands at 50 hours, 14 minutes and 25 seconds. Swinden and Withers set that mark in 1966, making the tandem Land's End - John O'Groats (LEJOG) one of the most durable records in cycling.
Irvine and Mitchell have got off to a storming start, covering the first 100 miles in 4:44:19, an average of 22.89 mph, according to their tracker.
It's Irvine's third attempt on the record after things went pear-shaped for him and his partner in 2012 and 2014.
In 2012, Irvine and Ian Rodd rode the full distance, but missed the record by more than eight hours after Irvine became ill early in the ride. They are thought to be the only team to have ridden the distance non-stop since Swinden and Withers.
In 2014, Irvine teamed up with time trial legend Glenn Longland, but things went south when Longland collapsed just before they reached the halfway point.
The tandem LEJOG has defeated other pairs of top-flight athletes too.
In 2011 James Cracknell and Jeroen Walters abandoned 68.3 miles from John O'Groats, citing safety issues.
That was Cracknell's second attempt at a LEJOG tandem record after a tilt at the mixed record in 2009 with individual pursuit Olympic champion Rebecca Romero had to be abandoned because Romero developed swelling around the knee.
A typical End-to-End touring ride takes about ten days, though riders doing it for fun usually take a longer route than the 832-mile track Irvine and Mitchell are following.
The solo men’s record is just over 40 hours (40:04:20, set in 2001 by Gethin Butler) so on paper the tandem record looks vulnerable, tandems usually being faster than solo bikes.
But as the record's recent history shows, a bike with two riders means there are twice as many chances for something to go wrong.
Irvine's previous experience and support team should increase the chances of everything going smoothly this time.
He said: “Charlie and I might be the ones riding the bike, but it’s a real team effort and a huge amount of work from everyone has gone into making this record attempt possible.
"I’m extremely grateful to the coaches at Winchester University who developed our training plan, the guys at Orbit Tandems who specially designed our amazing bike, our nutritionist and all the medics, route-planners and support crew who have given up their time to support the attempt, proof that success is a team game.
"With the dedication and training we've all put in, myself and Charlie have a real shot at breaking this record and we’re very excited to get going.”
You can follow the team's progress throughout the attempt on their live GPS tracker or follow them on Twitter at @a3crg, @DomIrvine and @cmitchell5017.
Acknowledged by the Telegraph as a leading cycling journalist, John Stevenson has been writing about bikes and cycling for over 30 years since discovering that people were mug enough to pay him for it rather than expecting him to do an honest day's work.
He was heavily involved in the mountain bike boom of the late 1980s as a racer, team manager and race promoter, and that led to writing for Mountain Biking UK magazine shortly after its inception. He got the gig by phoning up the editor and telling him the magazine was rubbish and he could do better. Rather than telling him to get lost, MBUK editor Tym Manley called John’s bluff and the rest is history.
Since then he has worked on MTB Pro magazine and was editor of Maximum Mountain Bike and Australian Mountain Bike magazines, before switching to the web in 2000 to work for CyclingNews.com. Along with road.cc editor Tony Farelly, John was on the launch team for BikeRadar.com and subsequently became editor in chief of Future Publishing’s group of cycling magazines and websites, including Cycling Plus, MBUK, What Mountain Bike and Procycling.
John has also written for Cyclist magazine, edited the BikeMagic website and was founding editor of TotalWomensCycling.com before handing over to someone far more representative of the site's main audience.
He joined road.cc in 2013 and these days he lives in Cambridge where the lack of hills is more than made up for by the headwinds.