“If we meet anything big, wait for my instructions,” says Allon. “Some people say, ‘Oh, I’ve been coming to Africa for decades.’” Well, you’ve never been to Congo, and if I say that buffalo is going to charge, it’s going to charge.”

It’s early in the day. The temperature hangs in the languid mid-20s, intensely humid. In the rainforest of Congo’s Odzala-Kokoua National Park, the silent struggle between life and death is in earnest. Fallen trees are overcome by bracket fungi and picked over by termites. Vigorous, spindly saplings shoot arrow-straight for the light. To stand still too long risks being composted.

Bordered by the Central African Republic, Cameroon and Gabon to the north, the Angolan enclave of Cabinda to the south, and the Democratic Republic of Congo in the east, there are easier neighbourhoods in West Africa. The Republic of Congo has a population of less than five million, most concentrated in the capital, Brazzaville, and second city Pointe Noir. Limited infrastructure has ensured vast tracts of its equatorial rainforest remain pristine. These steamy repositories of biodiversity are tough places to get to – and even tougher places to be. In north-west Congo, Odzala-Kokoua National Park’s 13,400 square kilometres lie at the farthest fringe of wildlife tourism, accessible only to a determined few.

The dense forest eventually gives way to bright sunlight and a cloud of orange butterflies at a riverbank clearing. “We can all swim, can’t we?” asks Allon. Lifejackets on, electronics stowed in dry bags, we haul kayaks to the water and enter the Lekoli River’s fast-flowing current.

Nick's group prepares to trek through the river to Lango Camp (Nick Redmayne)

Our destination is Lango Camp, a luxury campsite, and our plan is to kayak down the river as far as we can, then hike the final few kilometres across the bai, a local term for a clearing, to the camp itself. This is nothing like an east African walking safari, scout with elephant gun out front and deferential “tea boy” trailing behind. I’ve been in the country less than 72 hours and it’s clear that Congo doesn’t do Out Of Africa-style safari fantasy. Here, we have to work for our luxury.

We make quiet progress down the river, allowing the current free rein, paddling only when low-lying branches reach out to block our way. A pied kingfisher dives in and reappears, gripping a fish I’d be proud to have caught. Allon spots a troop of putty-nosed monkeys, and we paddle back for a closer look. They’re dark shapes high in the trees, making the branches shake with acrobatic leaps from one to another. “The animals here haven’t had much experience of people. They keep their distance,” says Allon. “There aren’t many tourists.”

Lango Camp and a bottle of gin are the reward at the end of the trek (Nick Redmayne)

Fighting the current, we make landfall to pick some wild limes – a request from the cook at Lango Camp. The fruits are in a prickly thicket but soon we’ve collected two fragrant bags to show for our scratches.

Back on the water, the river relaxes into a wider, gentler flow. A pair of hornbills make a low pass, left to right. “It’s a chimp!” calls Allon. A single ape – a lookout for a foraging group – has seen us too as he makes his way deftly through the treetops.

From the main channel we paddle into an expanse of slacker water, the beginnings of the Lango bai. Soon, it’s too shallow to kayak. We step into warm black mud, tie up the kayaks and squelch slowly across the bai, easier to follow a watery channel than to keep to ‘dry’ land.

A rumble resembling distant artillery fills the air. “Green pigeons,” says Allon. Ahead several hundred birds have taken to the air. They circle, land, and then explode into flight again. We climb onto an island where shards of pottery, some blackened by fire, litter the ground. “This place was inhabited once,” says Allon. By whom, he never tells us.

Through binoculars I survey the way ahead. Our route to the camp is blocked by a chestnut-brown herd of grazing buffalo. “We’ll go a little to the right. Carry your paddle low, keep a constant pace and don’t stop,” says Allon. We strike out, trying to keep a steady pace while knee-deep in stinking black mud. Two buffalo trot out from some long grass, looking a little too lively. “Come on, you know us,” Allon tells them. They hesitate, then canter off in the direction of the others.

Squaring off against local buffalos (Nick Redmayne)

Finally here’s Lango Camp, at the edge of the clearing. A pontoon lies at the end of a two-plank boardwalk. There’s a table and a cool box. On the table sits a bottle of gin. We have, of course, brought our own limes.

Congo’s wildlife headlines, if they’re written at all, focus on gorillas – in the northern forests, they’re more prevalent than people. The natural history of Odzala-Kokoua’s rivers, dense rainforests and open riverine bais, however, cannot be told by any one species. The accumulation of unpackaged wildness is remarkable. It’s an experience worth getting your feet wet for.

Worth the trek: the view from Lango Camp (Jonaston Boe/Odzala Discovery Camps Facebook)

Travel essentials

Getting there

Ethiopian Airlines (ethiopianairlines.com) flies six times a week from London Heathrow to Brazzaville via Addis Ababa from £712.

Staying there

The writer travelled as a guest of Farside Africa (farsideafrica.com) which has an eight-day Congo itinerary taking in Lango as well as two other Odzala Discovery Camps, from £3,550 per person. This includes full-board accommodation, domestic flights, walking and boat safaris, kayaking and two gorilla treks.

More information