Tomorrow husband and wife David and Katharine Lowrie, are due to reach the finishing line of a 6,400-mile journey which makes a marathon look like a jog around the block.
They will reach the shoreline of the Caribbean in Venezuela after running the length of South America.
The couple, both 35, have accomplished the astonishing feat entirely without any back-up team, taking turns to pull their supplies and gear in a two-wheeled trailer.
David grew up in Northumberland, where his parents Brian and Anne live in Longframlington.
The run has taken 15 months, and during that time David and Katharine have clocked up a fantastic list of firsts.
• First couple to run the continent. Katharine is the first woman to run the length of South America and David the first man to do so “unsupported”.
• First to run Bolivia.
• First to run the Amazon.
• First to run Chile´s mountainous road, the Carratera Austral.
A third of the run has been carried out barefoot or wearing special lightweight “barefoot” shoes. Ten pairs have been worn out.
They have usually run 20 miles a day, with the longest 35 miles.
When they started from Cabo Froward in Chile, it was winter and they faced snow and ice.
They estimated then that the run would be 5,000 miles and would take a year.
Their aim was to highlight the wildlife and habitats along the way and the threat from the growing human population and activities, from deforestation to over-fishing and climate change.
They have recorded more than 450 bird species as they have run through Chile, Argentina, Bolivia, Brazil and Venezuela and given talks to 1,000 schoolchildren.
Their journey has raised £5,000 for charities such as BirdLife International and Conservation Patagonia.
On the way they have had to cope with temperatures ranging from -10C to 45C, 100% humidity, snow, knee-deep mud, hurricaneforce winds and attacks by swarms of insects.
David was a pupil at Ford First School and Swarland First School in Northumberland, Dr Tomlinson Middle School in Rothbury and King Edward VI School in Morpeth.
He met Katharine, from Devon, at university and they married five years ago. They then set sail in a 50ft wooden former fishing boat for the Caribbean, where they spent two years on a seabird breeding census which became a book.
Then they sailed the boat to South America and began to plan the run.
They started training in earnest for the expedition in Uruguay, three months before starting the journey, including learning how to run using the bare-foot running technique.
David, who confirmed yesterday by telephone that they expected to reach journey’s end tomorrow, explained why they took on the challenge.
“We felt it was time we paid our rent for living on this extraordinary planet,” he said.
“ 10, 000 years ago the weight of the human population was one-tenth of 1% of all the Earth´s biomass. The rest was made up of wild animals.
“Today humans, our pets and domestic animals make up 96-98%. We decided to show how we all absolutely depend on the natural world and how amazing it is, and that with small steps we can overcome seemingly insurmountable hurdles, that time is running out, but it´s not too late protect it.”
Katharine said: “We both love running, it allows you to move through the countryside simply, quickly, quietly. Your emotions feel raw and alive.”
But the couple were never “serious” runners,. The longest they had run was 45 miles in a Peak District moorland competition.
Of the South American epic, Katharine said: “ It has been tougher than I could ever have imagined. “
David said: “But we have been offered food and shelter from the lowliest of night watchmen to one of the largest landowners . People clap as we pass and constantly stop to give us money in Venezuela. While in Bolivia, the poorest country in South America, people would run after us to ply us with drinks or grapefruits. We never expected this.”
David’s mother, Anne, said: “When they started it was bitterly cold and they had to cross icy rivers carrying their clothes, and then putting them on at the other side.
“The heat was also a problem and they had to start running very early, before the sun rose, because they could not run in the middle of the day.
“To do the journey unsupported has been amazing.
“People have taken them into their homes, they have let them sleep in their gardens, and they have camped on the edge of roads and forests. Poor people have given them food.
“They have been determined to do this and we have given them our support.”
The couple are due back in England on October 27 and will run into central London when they will meet Berwick MP Alan Beith.