This article presents a brief summary of the historiography of the British Empire in the second half of the 20th Century. It concentrates on three perspectives. During the second half of the 20th Century, the first two – the concepts of “informal imperialism” and “gentlemanly capitalism” – largely dominated the historiography of the expansion of the British Empire. The third – the British historian John Darwin’s description of the British Empire as an “imperial project” – is more recent. This article is centered on the second half of the 19th Century and goes up to the end of the First World War in 1918. It aims to judge the validity of the concept of an “informal empire” as a key towards understanding Anglo-Latin American relations, specifically Anglo-Mexican relations, during this period.