all mentions of extraordinary Indian diamonds in sources such as the Memoirs of the Mughal emperor Babur or the Travels of the French jeweller Tavernier have retrospectively come to be assumed to be references to the Koh-i-Noor. At each stage its mythology has grown ever more remarkable, ever more mythic – and ever more shakily fictitious. Yet anyone who tries to establish the facts of the gem’s history will find that unambiguous references to this most celebrated of gems are still, as Theo Metcalfe put it, ‘very meagre and imperfect’ – indeed they are almost suspiciously thin on the ground.