Neil MacGregor's world history told through objects at the British Museum arrives in Persia 2500 years ago. Throughout this week, Neil is looking at powerful leaders across the ancient world. Today he focuses on Cyrus, the first Persian emperor who created the largest empire the world had ever known. It stretched from Turkey to Pakistan and required a hugely sophisticated network of communications and control. At the heart of today's programme is a gold chariot pulled by four gold horses. This hand-sized model helps explain the rule of Cyrus, the "king of kings", and his ambitions for his vast territory - with contributions from the historian Tom Holland and Michael Axworthy of the University of Exeter. How does this glorious pre-Islamic past sit with the people of Iran today?