John Blashford-Snell not only exists, I have met him. In fact, I almost joined one of his expeditions to the Darien a few years ago.
Since I’ve got a lot of interest in the Darien myself, I’ve read several of the accounts of Blashford-Snell’s expeditions there too. As has been mentioned, he led a British Army group that crossed the roadless Darien Gap by car by hacking out a primitive road in 1972. (Not actually the first, as the article has it, but the second.) A few years later, he also led a trip to the site of the lost Scottish colony on the coast of San Blas at Caledonia Bay.
He came back to Panama a few years ago planning a trip to re-open some of the excavations at Caledonia Bay. I met him when he gave a talk on his plans at the British Ambassador’s residence in Panama City. He’s the kind of guy who talks entirely in anecdotes.
As it turned out, he wasn’t able to go back to Caledonia Bay because the Kuna Indians, whose territory it is, wanted to charge him exorbitant fees. Instead he did a trip to the Pacific coast of Darien. I was invited to go, but because of some missed communications wasn’t able to make it down there in time. It would have been interesting to say the least.