The mochileros are well organised and prepared for attacks - either from rival groups or the police.

“The guys at the front have big guns, like a long-barrelled Galil or a Mauser. Those at the end of the line carry pistols, like a Browning. Our lines are very long, and we walk with two or three metres between us. If there's an attack, it's the guys up front who fall first. When you're at the back and hear the shooting, you just run and escape.”

He says they buy ammunition from corrupt police officers. Often it is hidden in the buckets of food scraps and rubbish dumped outside the police barracks, from where the mochileros retrieve it.

But assaults and shoot-outs are not the only hazards. The journeys themselves are physically demanding, taking these young men high into the Andes on ancient Inca trails, and down into the Amazon Basin along tracks hacked through virgin forest. It can be treacherous.

“On one of the routes, you pass a mountain, and the drop to the river below is maybe 800m. You go along a path that's so narrow you have to walk sideways with your back against the mountain, carrying your backpack in front. Sometimes it's slippery, and people just fall.”

Daniel does not smile much. His face is quite immobile, even when he is talking. He is small and muscular, like a battle-hardened soldier, and he is old beyond his years. On every journey Daniel has undertaken, three or four mochileros have lost their lives.

“I've introduced family and friends to this business. We travelled together. But 10 of them have died. Some were close relatives, cousins with the same surname as me. It's very painful to leave your cousin behind on the trail somewhere.”

Of those 10 young men, four fell into the river, the others fell victim to minor injuries that meant they were unable to continue. With treatment they would have survived - but left alone, with limited food and water, they died.

“Maybe you get bitten by an insect, and get an infection. There are plants that can heal you, but they aren't available everywhere. Or you fall or get cut. Your feet swell, and they change colour. Then you can't walk. Your foot rots and ants enter the wound. You can't go on because of the pain. And there's no-one to help you - the others just leave you. That's how your life ends,” he says.

“You try to help them on the first day, but then you get tired and they have to stay behind.”

 In this line of work, nobody's responsible for [you], or cares, when you die.”

The fear of losing his own life has not yet persuaded Daniel to stop. The money is too tempting. He is paid $2,000 for every round trip - more if he takes his own weapon. It is a small fortune in the valley.

“If you think about the risks, then there are risks. If you think you could die, then you could die. But if you say no to those thoughts, faith moves mountains.”