On this final leg of his journey, Ben encounters the mighty Congo River for the first time. A trade super-highway, this great river allowed 19th century Europeans to plunder the resources of Central Africa and enrich their Colonial Empires - and it's still a lifeline for millions today.

Near the capital, Brazzaville, the Congo River transforms into the deadliest rapids on the planet, and Ben meets the daredevil fishermen risking their lives to put food on the table. He joins them on the edge of the banks where over a million cubic feet of water flow past every second. The fishermen dive into these fierce rapids to secure their nets, much to Ben's astonishment and concern.

The Congo's treacherous rapids led French and Belgian traders to build their respective colonial capitals on opposite banks of the river. Ben explores Brazzaville's French colonial legacy and meets the city's famous "Sapeurs" - African style-icons who mix Congolese fashion with French haute-couture. He visits a local market with "Congo's best dressed man", Sapeur Maxime Pivot, to choose flamboyant material for his next attention-grabbing outfit, before seeing the Sapeurs in action in a street fashion show.

European colonisation also left a darker legacy in the Congo, and Ben learns how conflict and chaos in neighbouring Democratic Republic of the Congo is threatening the stability of the region.

Ben's epic Congo journey goes out with a bang as he dives into the surreal, mad-cap world of Congolese wrestling, in which fighters use the ancient magical powers of "Juju" to defeat their opponents. He watches on awe-struck (and a little horrified) as grown men dress up as mermaids, set themselves on fire, brandish live snakes and eat glass bottles. As Ben says himself, it's "just another day in the Congo".

On this second leg of his journey, Ben heads deeper into the vast Congo wilderness to fulfil his life-long dream of seeing wild gorillas. He discovers a region experiencing rapid change: logging roads have opened-up the rainforest and thousands of people are flooding in to seek their fortunes. It's a threat to traditional communities who rely on the rainforest – but also to its stunning wildlife.

Ben visits a bushmeat market, where some threatened species are sold for food – and local stall holders don't take kindly to the presence of cameras. An angry trader confronts Ben and the film crew and demands they stop filming. The bushmeat trade presents a dilemma for Ben: it isn't illegal, and people here are struggling to survive, but it's clear the Congo's rich wildlife is under increasing pressure.

In a fast-changing region, Ben wants to know what other ancient customs are still surviving here, and at a traditional community he witnesses a scary and painful rite-of-passage ceremony for young men. Boys on the cusp of adulthood take part in a public circumcision ceremony, and in the days leading up to it they are deprived of sleep and insulted by members of the community to test how tough they are.

Finally, Ben heads to Ngaga Camp and a gorilla research station on the fringes of one of Africa's oldest national parks. He comes face-to-face with majestic wild gorillas and witnesses a rare close encounter between two huge 200 kilogram silverbacks. But he also learns the gorillas are facing a deadly threat from poaching, and meets the local heroes who'll stop at nothing to protect them.

On the first leg, Ben arrives in the bustling capital Brazzaville, before setting off on a gruelling two-day journey into the wilderness to visit a remote tribe living deep in the jungle – one of the longest-surviving cultures in the world.

The Mbendjele BaYaka tribe is semi-nomadic, living in traditional huts made from leaves, and they have never been filmed before. Ben throws himself into every aspect of daily life, building his own forest home and joining the women on foraging expeditions to hunt for food.