Two hardy British adventurers have walked, climbed and paddled for 83 days across one of the world’s wildest and least explored countries.

Patrick Hutton, 26, and Richard Johnson, 27, believe their’s is the first crossing of Papua New Guinea’s widest point, north to south, without any motor-powered assistance.

The men paddled rafts down crocodile-infested rivers, trekked through swamps and over mountains and used jungle vines to climb cliff faces as they travelled through one of the world’s most remote places.

They each carried almost 40 kilograms of equipment in the sweltering humidity and ate mostly rice and tinned fish.

On the expedition’s blog, Hutton wrote on May 2 after five weeks of travel: “A prevailing memory from the last 12 days will be the overwhelming insanity of our journey.

“Attempting to traverse one of the most formidable mountain ranges located between the Himalayas and the Andes has brought challenges which neither of us had contemplated.

“The communities which we are travelling through are connected by a cobweb of tracks, each trail more vertigo inducing than the one before.

“A large proportion of our days is spent rock climbing or as we affectionately term it, ‘route finding’, clambering over near vertical shingle.

“With our weighty bergans we are more cumbersome tortoises than agile mountain goats, and although we had anticipated rugged terrain, even our combined and varied travel could not have primed us for the coarseness which PNG’s Star Mountains present.

On June 2 Hutton wrote: “On our 83rd day, we’ve reached Daru! Finished! Completing, we hope, PNG’s first unmotorised crossing, at the island’s widest point.

“Exuberant doesn’t describe how happy we are.”

Interviewed by the ABC after flying back to Port Morseby Hutton said: “Originally we intended just to go up the Fly River with an outboard motor.

“Then Richard and I discussed it a bit and it evolved into something else – ‘let’s try the whole island, let’s try and do it without a motor’.

“Basically it got a bit out of hand.”

The 1600 kilometre trip began on Papua New Guinea’s northern coast at Vanimo, covering grasslands before encountering the steep Star mountain range to reach the Fly River.

There, two dugout canoes were lashed together to make a customised wooden catamaran.

On the expedition’s blog site Hutton wrote of the final day: “The mighty Fly River widened from two to 95 kilometres. Its channels, straits, currents and torrents form a mighty vacuum, the opposing edge never in sight.

“We were constantly on edge, waiting and expecting the boat to capsize, sending ourselves and our luggage overboard in an expedition stunting sweep.

“As we stepped out of the boat, we could not process our achievement, and as I sit here writing this, I am still in garbled shock.

“Two years of preparation, anticipation, fear and focus, the pinnacle of our plans is finally achieved.

“After four days of paddling through pelting, perpendicular rain, we finally saw what was to us, the most beautiful sight in the world – Daru Island.

"We remorselessly left our vessel, with little sentiment and no backward glance to the buoyant boat which had brought us in to the bay. Homing in on the first available beer, both of us felt extremely proud.

“In a dreamlike state I sign off our last post from this spectacular country, whose support, people, and idiosyncrasies have undoubtedly left us with one of the most surreal and hard hitting experiences of our lives.”

The trip was a fundraising effort for the international development organisation, ChildFund.

Hutton and Johnson form a strong team – between them they have summitted mountains in the Andes, cycled the length of China, navigated the entire Amazon river, filmed at extreme altitude in the Himalayas, climbed Kilimanjaro, cycled to Africa, trekked the length of Sri Lanka and cycled the length of Iceland.