Vietnam's Tarzan was raised in the jungle, cut off from civilisation for 40 years. Watch his amazing story here

In 2013, a father and son were 'rescued' from the Vietnam jungle, having spent 41 years there completely cut off from civilisation. Their incredible story begins as US troops bombed their village during the Vietnam War. Army veteran Ho Van Thanh had fled into the jungle, taking his baby son Lang with him.

Unaware the war ended, the pair remained in the jungle for the next four decades, moving further into the jungle every time nearby villages began to encroach. They survived by hunting and foraging, setting up treehouses to live in. But with Thanh's health beginning to fail, their way of life could not last. Eventually authorities found them and took them to the village where Lang's long-lost brother lives. You can read the full story of how they survived – and came to be rescued – here.

News of the 'Vietnam jungle men' spread fast and, in 2015, Alvaro Cerezo, managing director of Docastaway – which offers holidays to remote, uninhabited parts of the world – arranged to meet with Lang. Initially, he had hoped to find out about their survival techniques, but instead they ended up spending five days together, living in the jungle where Lang had spent most of his life.

Now, Cerezo has released a documentary about Lang, filming the first time he went back into the jungle. In the film, he follows Lang as they make their way through the dense foliage, talking about how Lang and his father lived – and showing how they would catch rats and bats.

When asked if he had ever seen other people in the jungle, Lang said over the 40 years, he came across just five others – and that every time he did he would run away and hide: "People could hurt me," he said.

Lang said there are lots of things he likes about the village now. He loves animals being friendly to people – in the jungle, he said, they would always run away from them. He also said he likes the light. In the jungle the only light at night comes from the moon – which Lang believes was put there with a long rope.

Lang's brother is now helping him adjust to his new life. While he struggles to tell the difference between good and bad and is very much child-like, he is happy living in the village and not being in the jungle anymore.

"It's been three years since Lang arrived in the modern world," Cerezo explained. "The first year was the most difficult for him amongst other reasons, because of health problems from the virus and bacteria new to his system. Nonetheless, we can confirm that Lang is happily adapting to his new life, mainly for the freedom he now enjoys."