Throughout this week, Neil MacGregor is describing power struggles across the globe around 3000 years ago, as ambitious new forces set about building sophisticated new societies - from the Middle East to South America. Today he describes what was happening along the River Nile and how a powerful new king conquered Egypt from Sudan. His name was Taharqo and he ruled from a vibrant new civilisation (in modern day Sudan) called Kush. These days few people even know that the mighty land of the Pharaohs was once ruled over by its southern neighbour. The evidence is summed up by a sculpture at the British Museum that shows the ruler from Kush as an Egyptian sphinx.