A London doctor will tomorrow embark on the ultimate long-distance cycle ride, planning to ride 50,000 miles over the next five years to raise £50,000 for the medical aid agency, Merlin.

That’s getting on for three times the distance that the likes of Mark Beaumont and James Bowthorpe have ridden in setting records for the fastest circumnavigation by bike.

Dr Steve Fabes, originally from Oxford, who works at Guys and St Thomas’s Hospitals, aims to ride the length of six continents during his trip. On his way, he plans to pass through regions hit by any of 14 tropical diseases typically found in poverty-stricken areas and which affect up to 1 billion people around the world, and will stop off at centres run by Merlin.

The 28-year-old told the Oxford Mail: ‘This is the opportunity of a lifetime and knowing that I’m fundraising, which will make a huge difference to Merlin, spurs me on. Still, I am absolutely petrified and excited in equal measure.”

During his trip, Steve will pass though 60 countries and spend up to 1000 days in the saddle, riding his custom-made Santos Travelmaster through terrains as diverse as the Arctic and the Sahara, and he acknowledges that facing those extremes will be a supreme test of his endurance.

“I have been so busy preparing for the trip that I haven’t really thought much about it. But when I get going it will be a big challenge for me, which will certainly push me to my limit. I’m just looking forward to getting going now.”

This isn’t Steve’s first long-distance trip, however. In 2000, he cycled the length of Chile, from Patagonia in the south to the Atacama Desert in the north, together with his brother, an expedition that took five months.

Carolyn Miller, chief executive of Merlin, said: “It’s a long and extremely arduous and ambitious route and we are honoured that Steve choose Merlin as his charity of choice. All fundraising will help us deliver vital medical aid to people caught up in conflict, natural disaster and health system collapse. His support is literally life-saving.”

As part of his preparation for his trip, Steve went through a number of mental and physical tests which will be repeated when he eventually gets back home, enabling medical colleagues to gauge the impact of his long-distance trek.

Before embarking on his journey, Steve received backing from a cyclist famous for covering rather shorter distances, four-time Olympic gold medal winner Sir Chris Hoy, who said: “This is a hugely ambitious and inspirational challenge that will surely test Steve’s resolve and determination to the limit.”

More information is available on Steve’s website at www.cyclingthe6.com, which also has a link to his page on the Just Giving for anyone wishing to make donations. He’ll also be updating his blog and tweeting his progress on Twitter, uploading pictures to Flickr, and there is even a Facebook fan page.