Back at the beginning of August, I used my summer holidays to play ‘tourist’ in London. My first stop was the Tower of London and, among the ravens, armour and tales of bloody executions, I popped in to see the Crown Jewels. At that point I was already aware of this new history of the famous Koh-i-Noor diamond and wanted to see it for myself. I discovered, as many have before me, that its legend casts a far larger shadow than its reality. Indeed, it looks almost modest alongside the Cullinan I Diamond that sits atop the monarch’s sceptre, or the Cullinan II in the Imperial State Crown. So what was it about this rather unassuming diamond that captured the imagination of generations? With Dalrymple and Anand as my guides, I embarked on an engaging tale of blood, war, ambition, extravagance and conquest.