Within it is a fraction of the Ho Chi Minh Trail, the network of camouflaged roads along which North Vietnamese forces transported troops and supplies to the south during the American War, and deep in the unexplored interior are endangered species including cloudy leopards and black bear.
At the national park headquarters in the provincial capital, Ban Lung, an establishment whose grandiose scale belies the fact that salaries have not been paid since the development budget ran out, we pack up faux-US Army camouflage bedding and embark on the trip to the boundary.
Two hours on the back of a bike over dirt roads less rutted than cratered is either a pain in the butt or an exhilarating rollercoaster ride depending on one’s age and confidence in the protective capacity of Cambodian helmets.
As the driver accelerates down a 1 in 5 gradient, over a rough plank bridge, swerves past a bike laden with paddy straw and floors it for the uphill stretch, I am painfully conscious of fifteen badly packed kilos hanging off my back.
At the Tonle San river, where local kids splash on sand islands and cows graze the steep green banks, we pile into a longtail boat. Our sixteen-year-old boatman hauls on the starting rope, and the engine bellows into life with nary a stutter.
It’s a dazzling journey, the lazy curves of the river backed by acid-green leaves, the whitened bones of dead trees, viridian bamboo, soft heads of pampas grass as high as a house, slender reeds bowing to the golden water.
We ground on sand shoals, disembark and wade through the current, then take to the bank for a set of rapids which our boatman handles with insouciant style, gunning the boat savagely up a sinuous water slide, the long propeller precision-placed in water that can’t be more than a foot deep.
Wonara, the ranger, looks on nervously. After a couple of nasty scraping sounds and some unscheduled jolts on the next few rapids, the chubby, sweet-natured face beneath the suede cowboy hat is sweaty.
Wonara is twenty-three years old. This is his dream job. And he takes it very seriously indeed.
Swinging into the force of the final rapids we meet another longtail soaring down at speed, its passengers’ mouths wide with exhilaration as it swings round away from the bank and into our path.
Wonara leaps overboard, pushing our boat backwards, and swipes at the side the approaching boat, swinging it round and onwards with the force of the water. I catch a glimpse of the exhilaration turning to shock as the boat races into the distance.
Our boatman, unmoved, negotiates the rapids, pulls in at the bank and awaits the return of Wonara, who celebrates our narrow escape with an Alain Delon cigarette, still the nicotine of choice in the former IndoChine.
“My phone no work,” he says. “But I am happy. One time this happened on a boat, the boat broke apart, and a child from the tribal minority hurt his back, his head. He was in the hospital for one week. You see,” he says, nodding at Z, “I am always taking care of him.”
“That was a real Indiana Jones moment,” I say. He hasn’t seen the films. His taste runs to Chinese martial arts movies, with a Cambodian star.
Nor, I establish, has he seen a film with Alain Delon. The great man exists, in Cambodia, only as Delon, the premium alternative to Fine.
We spend the night in a Brao village on the fringes of the park, six wooden houses on stilts occupied by 50-odd Brao speakers, 20-odd pigs and piglets, several vocal cockerels and a harem of hens, plus a range of short-legged, barrel-chested hunting dogs.
Even the smallest of the houses, where an extended family sleep in a space not much larger than a London bathroom, boasts a pristine yard, the infertile sandstone soil brushed to a Zen smoothness.
A compact, muscular man, with deep scars on his legs and chest, sporting Liverpool shorts and rubber sandals, enters the guesthouse with a confident air and holds out his hand. This is So, deputy chief of the commune, and our local guide.
So is profoundly deaf after a stint manning heavy artillery for the Lon Nol forces in his early teens, and communicates with us in a mixture of English letters scratched in the dirt with a stick and a fluent and evocative sign language.
“He learn in Vietnam,” Wonara explains. “He go to Vietnam during Khmer Rouge time, and he learn Vietnam letters, English letters, not Khmer letters.”
I am marvelling at the scale of a corpulent pink porker, two or three times the size of the darker hogs around it, though still petite compared to Western hogs, pen-fattened on antibiotics and super-charged feeds, or pampered on organic delicacies.
How old is the big pig, I ask him, holding up fingers and making a questioning face. He holds up four fingers.
I hold up five fingers, raise my eyebrows questioningly and make a throat-cutting gesture: will they kill the pig next year?
This is the funniest thing that So has “heard” for a while. He shakes his head vigorously, bends double laughing, cups the pig’s balls dramatically, and indicates, with an expansive and explicit gesture, that this here hawg is the village stud, and definitely not for eating.
“The pigs are very important, not for eating, but for religion,” Wonara says. “When someone gets ill, or someone die, the shaman tells them make a sacrifice. Maybe a buffalo, maybe a chicken. Most often a pig.”
So coppices long sticks, arrays them between three cooking stones, and boils water for rice. Z explores the flammability of bamboo papyrus.
We sling our hammocks in the guesthouse and wash in the river.
I don’t have the local skill of preserving modesty with a sarong while washing, plus it’s quite hard to work out which bits I should be covering. One of the village grandmas is wearing her bare breasts and a sarong around her waist, yet keeps her legs firmly covered. I play it safe and go in fully clothed. Z, like the village boys, goes naked.
As night falls and the cooking fires are extinguished, the unmistakable sounds of three toddlers refusing to go to bed echoes through the jungle, interspersed with grunting, intestinal, rumbling noises from the pigs below the floor.
The roar of a late-arriving longtail boat is followed, incongruously, by the excited revving of a scarlet motorcycle, which whizzes up from the riverbank carrying a young man, his lady, in hot pants and top tailored to match the vehicle, and a couple of cases of what looks like beer. She is riding side-saddle.
The bike belongs to the family in the big house, whose dust yard has a few lilies around the border, and whose roof is adorned with the colourful prefabricated architraves favoured by country folk who have done well. One of the family is a bigwig in the provincial government, says Wonara, and the children go to school in town.
“They buy this one week tomorrow. I say to them, ‘Why you buy this? Are you crazy? There is nowhere you can go on this,’” says Wonara. “They say they have family in the city and they want to be like people in the city, so they buy a moto, like people in the city.”
Over the course of the night, this status purchase will make the 100-yard trip from the riverbank to the village and back again seven or eight times, fuelled by the eternally combustive mix of beer and adolescent hormones, and kerosene from a plastic bag.
Later, we hear gunshots, two only, in quick succession. Wonara, who has carefully explained to us that the tribal minorities hunt only with crossbows and that guns are not allowed in the park, looks alarmed. “Maybe military,” he says. “Shooting at loggers, maybe. Or border.”
Given the absence of crossfire, and the prevalence of “wild meat” and “wild pig” on menus in Ban Lung, hunting seems more likely.
“Next day I make a report, then it goes upstairs,” says Wonara. “The big man will decide. It for military to fight with poachers. We have no guns.” His forlorn expression suggests the paperwork is utterly pointless.
As we set out in the morning, So takes one look at Z’s physique, cackles, and mimes a piggyback. I shake my head. He’ll be walking, I mime, waggling my middle and index fingers.
So is not convinced. This is, says Wonara, the first time a Western child has gone into the park, which explains why half the village turned out to watch Z changing into his pyjamas the night before.
We pass a 120-foot tree, its branches well above the canopy, with a ladder of bamboo pegs hammered into the trunk. “The people climb for mynah birds, looking for baby birds,” Wonara explains. “They can talk like people, say anything at all, they take them to be their friends.”
A few minutes downstream, bored soldiers lounge in hammocks, smoking. One sits on a chair, his rifle between his legs. They wave us through into the park proper, where the Brao are allowed to forage and hunt, but no longer to slash and burn: the government moved the village when it created the park.
We stop at the dense, burnt-black trunk of a tree, with a neat basin carved deep into the rutted bark, filled with a murky, golden fluid. “Oil tree,” Wonara says. “The Brao use it for torches.”
To Z, this is manna from heaven. He experiments with torches — sticks, leaves, bamboo, combinations thereof — while Wonara becomes increasingly twitchy. Once he gets to moss, I suggest that he continues experimenting at the next oil tree we reach.
We pass civet droppings and wild boar tracks, see birds of prey spiralling above the canopy, sample citric, refreshing leaves which the Brao use for medicine, and carve wood from a tree to make a tea that covers the earthy, organic flavour of boiled river water very pleasantly indeed.
Yet it’s less about wildlife — Cambodia is not safari country, after all — more about the chance to see a beautifully tuned ecosystem in action: the tiny thread of a new shoot germinating from a fungus growing on the trunk of a tree killed by a luscious, dark green vine, giant termite citadels atop dead roots, the bayon tree with its vertical, wedge-shaped roots wrapping its sinews around its dying partner, ants filing neatly around a four-point flower of palest pink with an explosion of stamens like fibre-optic disco lights, delicate fractals of lichen growing in symbiosis with woody mushrooms large enough to sit on, if you are nine.
Oh yes, and oil trees, obviously. “Look! It still burns even when it’s tarry,” says Z, at the fourth one we reach, smearing soot onto moss, his face and his jeans in roughly equal quantities.
“We need to walk faster,” says Wonara. “It is three hours more to the place we have lunch.”
Amidst the pyromania, Z has been not-so-quietly coveting So’s knife, a lethally curved machete-type affair known as a nyop, balanced to slash and carve on the angle. If he walks fast, I say, I will ask So to show him how to use the knife tonight.
The bribe works.
We eat lunch by a little waterfall, where a stream flows in three stages down a basalt face to a pool deep enough and calm enough to swim in. Azure and cerise dragonflies chase each other above the surface, butterflies in shades of yellow, turquoise, russet and scarlet flirt amid the rocks, crickets chirp in the leaves. It is idyllic.
Later, we join the Ho Chi Minh Trail, or, more precisely, Ho Chi Minh Trail Number 29, flatland cleared out of the jungle with the precision of a Roman road. Tall bamboos have filled the space where the trees were cleared so long ago, and slim the walk to a path no wider than the nigh-on invisible track we have followed.
For all the beauty, this must have been a terrifying place to fight, in the sticky mud of the wet season or the clammy heat of summer, its concealed network of trenches, bunkers, hospitals reeking of sweat, the forest littered with mines.
We stop at a pile of war junk, rusting artillery, plastic rifle butts, all working parts long cannibalised, the fragmentary remnants of a heavy machine gun that once bore a swastika. Z wields this long-dead weaponry with vigour.
The autumnal leaves inch-deep on the ground remind me of a Robert Capa picture, a wounded American soldier, his buddy dragging him to the medical station, in a landscape wiped almost flat by airstrikes and artillery, yet still, from the leaves and a handful of trunks, recognisably once a forest floor.
We leave the trail, and pick up a stream bed, scrambling up a valley over slippery rocks and damp mud, Z fiercely independent, brandishing the bamboo pole which So has cut for him. He makes impressive speed over the next two hours, scampering up and down hillsides, barely breaking sweat, while I curse my inability to pack with balance.
Our camp is a clearing. We sling hammocks on frameworks of old boughs, bamboo poles and living trees. So cuts a stem of bamboo. He carves the joints into drinking cups, slits the bark into curving slats which he places on a wood frame as a cooking table, and takes a long joint to the stream to carry water.
Z wields the nyop with a vigour that worries me and amuses So. “It’s just like a hatchet, mum,” he says. “I’ll be fine.”
He takes a vertical swing at a section of bamboo, positioned uncomfortably close to his foot. I realise how very far we are from any form of medical care, however basic.
“Watch how So does it,” I say. “You need to cut at an angle, not straight down.”
“It’s fine, mum,” he says, assaulting more bamboo.
“I’m not sure this is the best idea,” I say weakly. “I think you’re too tired to be using a big, heavy blade like that.”
“I’m not tired,” he says, yawning.
“And you don’t know how to use it,” I say.
This is a red rag to a bull. “It’s just like a hatchet, mum,” he says. “I told you already. And I’ve been watching So for the last hour. So of course I know how to use it.”
It is an argument he cannot win.
When the sun goes down, the frogs start up. It’s less of a frog chorus than a football crowd, competing chants at a range of pitches belting out across the woodland. We sleep early and, at dawn, hear the soft whoop of gibbons in the canopy.
On our third day, we pass a hole which a brown bear has carved into a tree trunk. “He look for honey, insects,” says Wonara. “He is good at climbing.”
A wild pig has dug up the roots of a sapling, looking for tubers and grubs. We find a tree the Brao use for stomach complaints and antiseptic, with a russet, scaly bark that brings to mind cinchona.
And, on the banks of the Tonle Sap, where we eat our lunch, we find bamboo poles, pre-cut for a raft. Z lashes four together with river grass and vines. They take his weight! They do not break! He idles on the current on a raft he has built himself.
“You know,” he says. “I think I might send an email to my friends quite soon. I don’t like to brag, but if I did brag I would brag. Anyway, I’ve most definitely got something important to report. It’s not often you get to build a bamboo raft.”