Via Gresham College, a series of lectures on the Victorian era by Professor Richard J Evans FBA. Below is the episode on Empire and Race:

Science and religion came together to help shape the attitudes of the British and Europeans towards the rest of the world, whose inhabitants were increasingly regarded as socially inferior and spiritually ignorant. This lecture looks at how these ideas framed the growth of overseas Empire in the latter part of the nineteenth century, how Britain and those European states that possessed colonies governed them and what were the consequences for politics and ideology at home, above all in the growth of the Social Darwinism, racism and extreme nationalism that led to the end of the ‘Victorian’ era in the First World War.

Other lectures in this series, The Victorians: Culture and Experience in Britain, Europe and the World 1815-1914, include:
Time and Space
Art and Culture
Life and Death
Religion and Science
Gender and Sexuality