A feast of pizza on the night before he went hiking may have contributed to the miraculous survival of the British backpacker Jamie Neale, who returned to civilisation on Wednesday after wandering for 12 days in the Australian bush.

The 19-year-old, whose father Richard Cass had given him up for dead, told his father yesterday that he had enjoyed a meal of several pizzas at his youth hostel in Katoomba, west of Sydney, before setting off into the Blue Mountains on July 3.

Paul Luckin, an Australian survival expert, said that the carbohydrate and calories from the pizza would have given Mr Neale the short-term benefit of an “extra burst of reserves”, enough to last him up to two days, although after that hunger would have set in. “You can’t say he survived because of the pizza but it would have helped him a bit,” he said.

Crucial to Mr Neale’s survival was the fact that he was able to find water in the creeks of the mountain range and thus avoid dehydration, which would have led to dizziness and the danger of falling in the craggy landscape.

In the near-freezing temperatures of the Australian winter, cold could also have killed the backpacker. “He needed to stay dry,” Mr Luckin said. “If he had got wet during the night and been unable to dry off, then hypothermia would probably have killed him.”

As the days went by and teams of Australian rescuers searched frantically to find him, Mr Neale kept going by eating seeds and grasses, a far cry from his usual teenage diet of fast food. He had packed nothing more than two bread rolls and a 600ml bottle of water in his backpack before he set off.

Yesterday, in hospital in Katoomba, he tucked into a hamburger with all the trimmings.

“He had a burger after the medicos finished with him,” Mr Cass told the Seven Network.

“He is eating anything the hospital can offer him,” said his doctor, Raul Amor, adding that Mr Neale was in a stable condition and doing remarkably well considering his ordeal. The backpacker, who was suffering from dehydration and exposure when he was found by Australian campers, remains on a drip and has scratches to his upper body but no other injuries.

Despite suggestions from some quarters that Mr Neale may have faked his story, those treating him, as well as survival experts, believe his account of events.

“Yes, I do believe him,” said another survival expert, Tim Tranter. “It’s not a huge issue to stay alive physically for 12 days. He’s young, strong and male. In situations like these, it’s moral durability that gets tested and it looks like he kept his spirits up.”

“It's an incredible story and that’s always harder to digest than those that turn out poorly," said Superintendent Tony McWhirter of the Blue Mountains Police. “There's nothing at this stage to say what he has said is not right, nothing at all.”

Mr Cass, who had been about to fly back to England after performing a farewell ceremony for a son presumed dead, said that he had been to hell and back. Mr Neale is expected to be released from hospital tomorrow.

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