Less than 100 years ago, the British ruled a quarter of the planet and one in five of the global population. Once, people were proud to call themselves imperialists, but now, to many, that seems like a badge of shame. In this Timewatch guide, David Olusoga examines not whether the British Empire was a force for good or ill, but rather how it has been portrayed on British television over the last 70 years. Drawing on decades of the documentary series Timewatch, plus many other gems from the BBC archive, David sees how Britain's Caribbean colonies grew rich on slave labour, how chaos gripped India post-independence, and how Africa was plundered for her mineral wealth. David investigates how film-makers through the years have represented the actions and legacy of Britain's period as the world's ultimate superpower. It used to be said that the sun would never set on the British Empire - now, long after it's gone, the arguments surrounding it are very far from being settled.

• Alice Roberts