In the third and final part of the series, Alastair Sooke charts the decline and fall of the Roman Empire through some of its hidden and most magical artistic treasures. He travels to Leptis Magna in Libya shortly after the overthrow of Gaddafi and finds one of the best preserved Roman cities in the world and the cradle of later Roman art. Sooke discovers glorious mosaics which have never been filmed before, but also finds evidence of shocking neglect of Libya's Roman heritage by the Gaddafi regime. His artistic tour takes him to Egypt and the northern frontiers of the empire where he encounters stunning mummy paintings and exquisite silver and glassware. As Rome careered from one crisis to another, official art became more hard boiled and militaristic and an obscure cult called Christianity rose up to seize the mantle of Western art for centuries to come.

• Alastair Sooke

• Alastair Sooke