Season 2, Episode 5 The Belgian Congo in the 1920s and 1930s.

After World War 1 the Belgian Congo's place in the world was
settled internationally.   The authorities, with private
backers, invested in the wealth opportunities presented by copper,
diamond and other minerals to increase revenues. 
Infrastructure projects were completed to connect these mining
areas to the Atlantic, and some Congolese were able to seize
opportunities within the system.  But for the majority this
was not the case, and rising tensions were palpable.