Swinging elegantly from tree to tree through the steamy jungle like an auburn sack of knuckles, is there any primate more revered and beguiling than the orangutan?

Despite their huge muscles and undoubted strength, the vulnerability of these ginger beasts tugs at our heart strings and with a fast-eroding habitat they can only be found on a couple of islands, Borneo being one.

That’s the very reason so many people make a pilgrimage half way across the world to watch these gentle giants.

Our journey to encounter these captivating creatures took us to Sandakan, a slightly unpromising little town in north eastern Borneo.

With an airport more akin to a London bus shelter and a diminutive town centre, it remains without doubt orangutan city - a stepping stone for the treasures of the island’s rainforests.

Any orangutan finding trip tends to be made up of two parts: a trip to Sepilok Rehabilitation Centre and a visit to the Kinabatangan River (A whole host of forest and jungle lodges have sprung up around Sepilok to cater for orang-tourism).

We stayed at Sepilok Jungle Resort which has a happy balance of cute wooden shacks and creature comforts. Getting from the rooms to the restaurant (which served amazing and ridiculously cheap Malaysian and Chinese favourites) and other amenities is an adventure in itself, involving a breathless clamber across various wooden walkways through lakes and trees. And although there was a cracking swimming pool, only marginally spoilt by rowdy youngsters, there are better places to relax – we were here for the wildlife. Sepilok itself is a bit of a weird one: you do get up close and personal with your favourite primate, but there is definitely a zoo vibe about it, with people taking pictures, shouting “monkey” and so on.

That said, as we were leaving, a curious orangutan swung down on to the walkway about a foot away from us, which was pretty incredible until the hordes turned up with their cameras.

Other Sepilok attractions include the world’s first sun bear sanctuary, run by ursine-enthusiast Wong Siew Te and packed with the cute little chaps; and the informative Rainforest Discovery Centre, with a canopy walkway for flying squirrel spotting.

But the other half of the trip is more enticing – the mighty Kinabatangan River, a brown, gloopy expanse of water home to an extraordinary selection of animals.

Reached by a three hour slog through endless palm oil plantations, via the Gomantong Caves – an enormous natural cathedral, home to millions of bats, a unique smell and ingredients for the best bird’s nest soup – followed by a boat trip; by the time we got to our cabin we felt like we had gone feral. It’s hot – very hot – and muggy, and when the lights go down the sound of the crickets is deafening.

River safaris are typically done at sunset and sunrise – the cooler weather meaning the animals come out in force.

Sunrise in particular is a magical time: morning mist rises gently from the turbulent depths as hordes of long-tailed macaques gibber and squawk, humorous proboscis monkeys – found only in Borneo – hop around though the trees and crocodiles bask in the sun.

But the main draw is the orangutan. You do have to use binoculars, but it’s much more exhilarating to see them in their natural environment. We were lucky enough to spend an hour watching a mother with her baby, relaxing in the crook of a large tree; breath-taking stuff.

When the sun goes down, another highlight is the night safari. Make no mistake, it’s a sweaty, leech-infested experience but the rewards are well worth it. We saw a mouse deer and various spectacular birds – pick of the bunch was the elusive Western Tasier, an amazing, doe-eyed creature that can spring from tree to tree without seeming to move a muscle.

The whole Kinabatangan experience involves a lot of heat, insects and minor annoyances, but that only makes it feel like you have earned the right to see these amazing beasts.