The British-born pair, who both teach at Malvern College Hong Kong, spent months linking various hikes and scrambles, most of which were well off the beaten path, with swimming in between.

Ross said putting the route together had been an “incredible experience”, but also cautioned against people who weren’t prepared taking it on.

“You don’t want to put people off, but at the same time, you don’t want someone to get seriously injured,” the 45-year-old said. “You don’t want someone to kind of do it and they don’t know what they’re doing.”

The main four recognised trails in Hong Kong – the 100km MacLehose, the 78km Wilson Trail, the 50km Hong Kong trail and the 65km Lantau Trail – are complemented by dozens of other smaller offshoots.

The 100km Argyle Ross starts in Kat O, in the remote northeast corner of Hong Kong. It is the only village in the collection of islands called Double Haven, a stunningly peaceful isolated sanctuary.

You have to hike and swim between the islands to get to section two.

Hong Kong’s 5th major trail commemorates late legend Nic Tinworth

Once on the mainland, the next 11 sections combine swimming, coasteering, and stream-hikes up waterfalls with intimidating names such as Stone Dragon, Flying Ape Gorge and Dragon Ball.

“There’s one on a stream called Ghost Anger,” Ross said. “It’s a really narrow, dark, flat stream. It’s not very interesting at all. When you can go along this stream for about an hour, you’re thinking ‘OK, fair enough’ – there’s no pools to swim in or anything like that.

“And then all of a sudden it just opens up and there’s this huge waterfall. And then you have to go up this cliff and at the start it’s OK. But then at the end there’s a bit of rope. You’re looking down and thinking, ‘I have to keep my wits about me here’.”

On the route’s website, Argyle and Ross have rated each section for difficulty out of five. The Kwun Wat to Tuen Mun leg they consider the easiest part, with beach swims and walks for less-experienced hikers wanting to get a flavour.

And as well as the beauty of the countryside, the route also weaves in and out of cultural points such as restaurants.

“We love doing a hike and at the end having a beer or some foods because you’re obviously absolutely starving,” Argyle said.

“So we wanted to, as much as possible, try and end where there would be a nice pub or a bar or a restaurant, but also somewhere unique, somewhere different, going with this whole trend of the trail being very, very different to the other ones.”

One section finishes on Route Twisk at a dim sum restaurant, and another finishes in Sham Tseng near a famous goose restaurant.

The pair came up with the idea when hiking last June. They started to mentally map together all the parts they’d done and the rest followed. The first half was very familiar to them, but the second was new territory.

“The west was a little bit like the wild west. We had to question different bits – is this going to work?” Ross said. “That’s what I loved about it because I’ve been here for 12 years. I’ve hiked the whole of Hong Kong, but it just introduced me to so many surprises.”

Even the parts they were familiar with became hairy at times. Near Pat Seng Leng they lost their way

“It was getting dark and we thought ‘OK, well this is a bit of a problem now’,” Ross said. “And Jack’s quite gung ho about things. So he says, ‘oh, let’s just bushwhack’.

“We’re 630 metres up – if we try to bushwhack, it’d probably take about a week, and it’ll be a helicopter rescue, without a doubt. But we did, we managed to find the ribbons [marking the trail] again.”

With that experience in mind, the pair have tried to design the route so it is unique and challenging, but not so hard to navigate.

The record for running the 100km MacLehose Trail is under 11 hours. Argyle and Ross think it would take at least six days to do their route in one go. But because of the need to scramble and swim, the camping gear would have to be minimal; things such as hammocks.

“You can’t rush the streams. It’s dangerous. You’ve got to take it slow. The swims slow you down. It moves it from maybe a four-day into a six-day minimum, maybe even seven-day thru-hike,” Ross said.

Argyle added: “It’s tough. And you kind of have to have the right weather as well, because [of the streams] you have to have some pretty clear weather for that week. So it’s not an easy window to find, which obviously makes it even more tough.”

The pair are currently concocting some awards for the first people to do the whole trail and the first to thru-hike it, without going home, to mark the achievement.

“This is a difficult trail,” their website reads. “For those that love water and seek real adventure beyond anything else offered by other long distance Hong Kong trails.”