"To anybody else, it's just a bike," says Josh Quigley. "But, for me, it's the vehicle for saving my life."
After losing his father to leukaemia in 2018, and then slipping into depression, Josh made plans to complete a task he had failed five times before - to cycle around the world.
But this week, while stopping to rest in London during the first leg of his attempt, his bike was stolen.
The loss, Josh says, was "devastating" - but he has not given up hope of continuing his journey.
"I first tried to cycle round the world in 2016," he tells the BBC. "This was really my journey to happiness, that's what I always called it."
In 2015, after splitting from his long-term girlfriend, Josh was suffering badly with depression, and tried to take his own life.
"I crashed my car at about 70mph on the motorway near my home in Scotland," he says. "I was really lucky to survive.
"After that I thought: 'I'm going to do something about this.'
"I went to see Sir Chris Hoy speaking in Edinburgh and just felt inspired to go on a bike.
"At that time, I wasn't a cyclist. I was a couple of stone overweight, I was drinking alcohol four times a week - but cycling was my way of trying to get happy again."
Despite travelling more than 10,000 miles through 14 countries on his last trip - Josh, now 26, never reached his goal.
"I think it's fear that gets the better of me," he explains. "If I finish I know how big it will be and I think that's what holds me back."
Even though he did not complete his previous trips, Josh believes touring on his bike saved him - describing the journeys as "life-changing".
But after his father's death last year, Josh began once again to struggle with life in Edinburgh.
He decided to attempt the trip one more time.
"It's got me out of a dark place once before so I turned to it again."
"I started in Edinburgh a couple of weeks ago and then stopped when I got to London for a rest before heading to France," says Josh.
"I was staying at a hostel on Borough High Street. Usually I would have the bike inside with me but when I arrived they said I wasn't allowed."
Josh was staying for two nights. His bike was locked to a rack outside the hostel - but by the second day it had been stolen.
"To think it's gone is devastating," he says. "It's almost like I've been grieving for it.
"When I first got on the bike in 2016, I was in such a bad place and together we went on that journey.
"We've done over 15,000 miles together. It's almost like a human, the way I look at that bike, the love I have for it, what it means to me."
Josh, however, is remaining stoic.
"The more I think about it, if somebody's stealing a bike then they're probably not in a good place in their life.
"Maybe they need it more than me."
While a setback like this might have previously ended Josh's attempt, this time he is refusing to give up.
He has appealed for the bike's return, but knows his chances of seeing it again are "low".
Josh's focus now, he says, is "trying to get on another bike and continue".
He has begun raising money for a new bicycle, and while it might not have the same sentimental value - it would allow him to complete a journey that has been four years in the making.
"I'm going to do it this time," he says. "It's not up for debate - I'm getting it finished."