“I jump out of the Range Rover, and, as I’m taking the ladders off the roof, our doctor yells, ‘Look out, behind you!’ There’s a fer de lance snake by my foot. Small, brown, deadly. No antidote. The bloody thing strikes my boot, into the leather, just below bare skin. As it rears up to strike again, the doc leaps out with a machete and lops its head off…”

Meet Gavin Thompson, the army officer who, in the spring of 1972, led the first-ever successful vehicle expedition through the world’s most inhospitable terrain: the Darién Gap. Stretching between Panama and Colombia, the Darién was - and remains - diabolical: a 250-mile stretch of swampy, malaria-ridden jungle populated by deadly snakes and vampire bats. No bridges, no roads, no tracks, just a Britain-sized clump of impenetrable undergrowth, unmapped and unknown to any humans but the handful of tribes inhabiting the forest.

In fact, Thompson’s mission was even grander than conquering the Darién Gap. It was the first to drive the length of the Americas: 17,000 miles from Anchorage in Alaska to the southernmost tip of South America. Thompson’s team of six men and two Range Rovers - launched the previous year - was dropped by military Hercules into Anchorage in December 1971, straight into the depths of an Alaskan winter.