“In 1987 I had a strategy and followed 2,470km of the Ming wall,” he says. An accomplished marathon runner, he ran the entire distance with no support crew or modern communications.

“I stayed with farmers for over 60 nights – I called it ‘the great wall of friendship’ – but I was arrested nine times, deported once, I needed two passports and made three marriage proposals,” he says.

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Lindesay now lives in an old farmhouse at the foot of the wall on the northern periphery of the Beijing suburbs with his wife, Wu Qi (the one he proposed to three times during that second expedition in 1987) and their two sons. He admits his family is obsessed with the wall and are all involved in offering his popular WildWall weekend tours (wildwall.com), designed for visitors eager to explore a less trodden path.

“We like to say we are a family of wall-nuts; very eccentric,” he says.

With 21 million people in the Beijing area not far from the wall, the Lindesay family are not the only ones fascinated. No longer content with spending their weekends in shopping malls, these days many Chinese want to be outside, Lindesay says.

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“In the last 15 years, the Chinese have rediscovered the great outdoors,” he says. “We have witnessed the rediscovery of the Great Wall by Chinese people armed with WeChat. ”

This puts pressure on sections of the wall in terms of conservation and environmental degradation.

“Many are not sensitive to the fact that this is the world’s largest open-air museum,” says Lindesay, adding that Badaling, around 80km northwest of Beijing city in Yanqing District, is visited most. But even this area of the wall extends for 388km so there is plenty of room.

“There is something for everyone on the wall around Beijing, depending on how much time you have,” he says.

Five tips for enjoying the wall’s wilder side

1. Get fit. The former marathon runner suggests visitors acquire a basic level of fitness – and it’s not just required for walking along the crumbling ruins. “You may need to hike up steep hills through forests to really appreciate the immense effort the builders went to to occupy the high ground,” he says. The highlights of his own wild wall weekends are two 10km dawn hikes. Groups are typically four to eight people and are popular with Western visitors and expatriates living in China’s big cities.

2. Take your time. The Chinese name for the wall, Wan Li Chang Cheng, literally translates as the ‘Ten-thousand li (a ‘li’ is about 500m) long wall’ – but Lindesay suggests a more elegant translation might be the “endless wall”. He advises visitors to walk along it for at least a few kilometres.

“Given the story of the wall, I am surprised people don’t give it more time,” he says. Despite increasing popularity, Lindesay says the wild side of the wall is still considered “out of reach” for most people.

3. Get reading. There is no one Great Wall of China, explains Lindesay: there are at least 16, spanning 2,500 years of Chinese history. “To appreciate the story, you need to embrace archaeology, geography, history, military strategy and conservation,” says Lindesay. His tours aim to unravel the story of the wall – built to avoid open field battle with nomads from the North – in a systematic way and include his story of roaming beyond the wall to better understand the enemies it was designed keep out.

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5. Time your visit for the best light. Some visitors worry about air pollution but Lindesay says that’s improving – but try to avoid the height of summer. “We have had beautiful clear autumn days around Beijing this year.” Aim for dawn or early evening to best enjoy the stunning scenery. “When I stand on the wall at sunrise, it takes one hour and 20 minutes for the entire length of the wall to be lit up,” he says. “This is something not just on a map, it’s on a vast landscape and to see it at sunrise is the absolute tops.”