In the 1850s, the early days of legitimate commerce, several British traders had operated on the Congo coast, but by the 1880s, when the rubber boom kicked in, only Hatton & Cookson remained (although Edwards Brothers from Liverpool still supplied the Portuguese house of Castro & Leitao north of the Zaire River).
In northern Angola, small Portuguese firms had established themselves especially along the banks of the lower Zaire River, where many sheltered inlets offered opportunities to carry out a small trade in vegetable oils; but the rubber trade was concentrated on the coast (though later in Noki) and required stocks that small firms could usually not afford.
One reason the electrical authorities are so excited by this theoretical possibility, is that the hydro scheme at the Inga Falls on the Zaire River
could produce between 50,000 and 120,000 megawatts.
In these expeditions Blashford-Snell played a leading role, and was then asked to organise first the Darien Gap Expedition and then the Zaire River
Exploration in 1974.
According to Cann, the most successful Portuguese "brown water" naval operation was the securing of the Zaire River
, Angola's northern border with the troubled Democratic Republic of Congo, in the early 1960s, which blocked the infiltration of National Front for the Liberation of Angola (FNLA) insurgents into the territory.
Even tougher assignments followed: the first vehicle crossing of Panama's Darien Gap, in 1971-72, and then, in 1974-75, on the centenary of Henry Morton Stanley's trans-African expedition, he oversaw a 160-strong international team's scientific exploration of the 4,370-kilometre Zaire River
The most common in Risangani are the tolekas, (taxi-bikes) and the djubudjubus (dug-out canoe taxis) whose traffic has increased sizably on the Zaire river
. Likewise, private shipping companies have benefited from both the deterioration of the road system and of the decrease in traffic on the state-owned ONATRA river boats.
Projects include dredging the Zaire river
between Matadi and the ocean; reconstruction and maintenance of main roads, upgrading the railway network and providing a regular fuel supply to ships, trains and trucks.