In 1580, Elizabeth I lent money to Don Antonio, the Portuguese pretender, to aid the recovery of his throne from Philip II of Spain. As security, Don Antonio pledged a diamond: the thirty-carat, table-cut Mirror of Portugal. He recovered neither throne nor diamond, which passed into the English royal collection and returned to the Iberian peninsula when Charles Stuart made an incognito play for the hand of the Spanish infanta. Perhaps the Mirror was an unlucky jewel: the infanta turned the future Charles I down, so the Spanish politely returned the diamond, which Charles later reset in the crown of his French bride, Henrietta Maria. When the queen fled to Antwerp at the onset of the English Civil Wars, the Mirror was among the crown jewels against which she hoped to borrow money for the Royalist cause. Cardinal Mazarin swooped in, and the Mirror eventually found its way onto the person of Louis XIV, greatly to the discomfort of the impoverished Charles II. The Mirror remained part of the Bourbon royal regalia until 1792, when it was stolen from the Garde Meuble in Paris, never to be seen again.

The adventures of the Mirror are among the many fascinating tales that range across continents and centuries in this masterly book. Beginning in the mid-14th century, when the jewel Pliny termed ‘the most highly prized of human possessions’