This article by Conor Pope (Irish Times) provides an interesting view on the Irish love of tea and its relatively recent history and in particular how the (then) Irish Free State set about substituting its tea supply chain, away from the London tea market, to sourcing tea directly from suppliers in Rwanda.
At the time Rwanda was a French colony, thus making the international logistics (slightly) less complex given the wartime environment and the relative predominance of British colonial control of much of Africa at the time.