When Richard Cass abandoned all hope of seeing his son alive again, he wrote a valedictory letter to the Australian volunteers who had spent more than 10 days searching for the 19-year-old backpacker.

Cass, a teacher, was preparing to return home to Watford, Hertfordshire. He used the letter to pay a poignant tribute to Jamie Neale, the boy he thought he had lost in the Blue Mountains, west of Sydney.

“Last night I was unable to sleep,” he wrote, “so I have tried to put together some words to convey something of what my family have lost if my son remains unfound."

“There is much concern in my country about the behavior of young men, with...their perceived shortcomings blamed on family breakdown. James came from a ‘broken home.' I forgot to marry his mother and we ceased to live together when he was three years old. He was raised on a council estate in north London."

“But this was a teenager who was never in trouble with the police, who left school last summer with A-levels in maths, chemistry and history.”

His son had worked as a laboratory technician to raise the money for a trip before his degree studies began at Exeter University, Cass went on. He was a blood donor and a recipient of the Duke of Edinburgh award, “kind and courteous”.

However, Jamie was no “humorless paragon of virtue”, he said. The two of them had once visited the grave of Karl Marx in north London “just to get in touch with history”, and Jamie had planned to fly from Australia to Hanoi and Moscow to “call on Lenin and Ho Chi Minh”.

“I believe any teenager who can arrange his tour of the world around the brilliant conceit of tracking down the cadavers of communist dictators is uniquely unique and very, very special indeed."

“This is the boy that I suspect I have lost for ever. This is the diamond my country has lost in this tragedy.”

Janet McGarry, a youth hostel executive who helped in the search, said the letter had had a profound impact on her: “I wept when I read that.”

Cass had arrived in Australia on July 8, confident that his son would be found. But by last Monday police had begun winding up the search.

“With every passing day now there’s much less hope of finding your son,” Superintendent Tony McWhirter, the police officer in charge of the search, had told him.

Cass made his own final pilgrimage to the Ruined Castle, a rocky outcrop three hours from Katoomba in the Blue Mountains, where Jamie had rested on July 3 before setting off for the six-hour round trip to Mount Solitary. Cass had “made a little shrine for my boy”, he said.

Last Wednesday Cass was waiting at the airport in Sydney for his flight back to London when the police called. “We’ve got good news,” they said.

Cass danced around the airport, shouting at strangers: “They’ve found my boy, they’ve found my boy!”

It was a joyful end to an ordeal that began two weeks earlier when Jamie Neale, from Muswell Hill, north London, arrived in Sydney on a backpacking adventure.

On July 2 he checked into the youth hostel at Katoomba, the biggest town in the Blue Mountains, where he ate five medium-sized pizzas at the hostel’s free pizza evening.

The next day he left at 9.38am, dressed in jeans, trainers, a shirt and a purple jumper. In his rucksack he carried a pint of water, a camera and his passport.

He told nobody where he was going. He ignored every warning in the police brochure Think Before You Trek, a survival programme introduced last year after an Australian schoolboy died of dehydration in the area. He also shunned advice to take a personal locator beacon, a device offered free to walkers by the police. He even left his mobile phone on his bed.

The three-hour trek to Ruined Castle is simple, but Neale had bigger plans. He reached Ruined Castle at noon, chatted with a young Australian couple who took his photograph, then pressed on to Mount Solitary. He arrived at about 3pm, walked around the summit and descended as dusk gathered at 5.30pm.

On reaching the valley floor, he lost the track. He tried to retrace his steps but by now “he was completely disoriented”, said McWhirter.

Thus began his extraordinary struggle for survival. For almost two weeks he wandered the dense bush, trying to find a track out of the valley.

He drank from streams and ate a leaf called kangaroo tongue, along with berries and nuts. He spent nights sheltering under strips of bark on the valley floors, which held pockets of warmer air although temperatures often fell to zero.

His worst mistake was that he failed to “stay put”, said McWhirter: “If he’d just stayed near Mount Solitary we would have found him. But he kept moving.”

“I thought I was going to die,” Neale said later. But it seems he never panicked. Each day he tried to reach high ground to reorient himself; but when he descended into the valley he lost his bearings.

The alarm was raised in Katoomba on July 4, after he failed to turn up for a pre-arranged trip and his mobile and gear were found on his bed at the youth hostel.

Australia’s mostly voluntary rescue teams went into action, with 400 volunteers fanning out through the scrub at an estimated cost of nearly $816,600. During the search, one volunteer broke his arm, another was airlifted with dehydration, a third twisted his knee and another received lacerations to his face.

Finally, after 12 days of bashing through the scrub, Neale was spotted by two campers near Medlow Gap. “I’m lost,” he croaked. “Do you know the way to Katoomba?”

Astounded to see him alive, the campers fed him chocolate and energy bars before helping him back to Katoomba.

Jamie signed a media deal reported to be worth $160,000 before leaving hospital on Friday and holding a party for his rescuers. His agent insisted that most of the money would go to the rescuers.

Click here to read more on this story from The Sunday Times.