A round-the-world record – in spite of the wombats

After five and a half months and 18,000 miles, Londoner nears finishing line

When a cabinet-maker from south London set out to become the fastest man to cycle round the globe, many wrote him off before he started. But less than five-and-a-half months after James Bowthorpe steered his bike out of the capital on an 18,000-mile ride through 20 countries, he is days from taking three weeks off a record doubters called "unbreakable".

Now riding 160 miles a day through northern Spain, Bowthorpe, who is being sponsored by The Independent, is due to beat the mark set by the Scottish rider Mark Beaumont when he rolls into Hyde Park on Saturday. Speaking from his saddle, the red-haired adventurer was counting down the hours. "I just can't wait for it to be over," he said. "My mind is okay but physically I'm totally exhausted."

Bowthorpe, 31, has pedalled across four continents since setting off at the end of March. Taking flights over oceans, he has cycled unsupported, carting more than 30kg of clothes, gadgets and camping gear across deserts, mountains and along terrifying highways. His 5,000-mile journey through North America meant Bowthorpe cycled for seven weeks without a day off.

In a voyage fraught with danger, Bowthorpe came closest to disaster in Iran. "It was the worst half an hour of my life," he says. Five men in a car followed the rider in the dark before trying to drag him off his bike. Bowthorpe was rescued by a stranger with an army friend. "He said the men would have attacked me and taken my bike," Bowthorpe said. "He ran his finger across his throat, but who knows?"

Less perilous encounters have included a collision with a wombat in Australia ("You think they sound cute but it was like hitting a brick wall") and, on the outskirts of Sydney, a brush with a gang armed with kebab missiles. After a severe case of "Delhi belly" in India, Bowthorpe was forced to take five days' rest in Bangkok after losing a fifth of his body weight.

Actually, his bike started to show the strain in the United States. Riding through Kentucky, Bowthorpe noticed a crack in his pedal crank. But he was back on track within hours. "Someone gave me a lift to a bike shop," he says. "They didn't have the right part but the guy who worked gave me the cranks from his own bike. Some of the people I've met have been incredibly generous."

Bowthorpe is depending on kindness off as well as on the bike. He wants to raise £100 for every mile he rides, eventually donating £1.8m to research into Parkinson's disease. Motivated by the plight of his late grandfather, Bowthorpe spent two years before his ride volunteering for What's Driving Parkinson's, a research team based at King's College hospital in south London. "To raise enough money I knew I would have to do something really tough," he says.

His efforts have gained support in high places. When Lance Armstrong heard about Bowthorpe's efforts, the Tour de France star, who is a friend of Parkinson's sufferer Michael J Fox, the actor, gave him a shout-out on his Twitter feed. "For a couple of days I imagined him watching me with his arms folded, shaking his head at my technique," Bowthorpe says.

The "Lance effect" caused Bowthorpe's own Twitter feed to acquire hundreds of new followers, but with £53,000 in the bank, the cyclist still has a mountain to climb to reach his fundraising target. "The real work starts when I get home," he says. "I've got to build something concrete on what has for some people been quite an abstract thing. I've cycled round the world; now what?"

In the meantime, Bowthorpe can be forgiven for basking in the glory of his success. "I'm looking forward to my first cooked breakfast for a long time in Portsmouth and then it's the home stretch to Hyde Park," he says. "I don't know who's going to be there but I'm hoping for a small crowd. It would be a bit of an anti-climax to wheel in with a puncture and have to take the Tube home."

To follow Bowthorpe's progress, or to donate money, go to whereintheworldisjames.com

The spoils of a cycling tour

What can James Bowthorpe expect when he returns? The previous record-holder, Mark Beaumont, was an economics graduate from Fife before he set out to bag the biggest prize in endurance cycling. He faced a mugging in Louisiana and a night in an Iranian prison cell but cycled 18,000 miles in 194 days. Taking nearly three months off the previous record, his feat was completed in February last year. His video diaries formed the basis of a Bafta-nominated BBC documentary, and a corporate speaking tour followed sponsorship and book deals. Beaumont, 26, then tried a world record-breaking Atlantic rowing trip in June but his boat sank days before he started. Now, somewhere in Mexico, Beaumont is on a new adventure, pedalling from Alaska to Argentina.