The heartbreak diamond is only two inches in length, and shaped roughly like a heart. It is a red diamond, but divided exactly in the centre by a streak of white diamond. It is the only known case of such a jewel in the world.

The diamond’s strange appearance is not the only reason for its romantic name. Legend has it that this diamond has never been owned by one person for more than three years without moving on. Some of its owners have lost the diamond to thieves, fires and floods; others lost their fortunes and were forced to sell; and one simply woke up to find the diamond gone. But the diamond’s reputation as a heartbreaker has only increased its intrigue and value for jewel collectors.

This is the ninth high-profile theft by the so-called Phantoms. They have earned their name by stealing diamonds without damaging locks or breaking safes, as if they can pass through walls. Only one of their operations has ever been foiled, when German police intercepted phone conversations and were able to recover a valuable tiara.

The group are believed to operate from Istanbul. Police have advised that the diamond is likely to be transferred to their headquarters, and are working closely with the Turkish police to monitor all routes into the city.

True to form, the Phantoms have managed to steal the diamond without leaving a trace. “It’s amazing,” said Stephan Dupont, manager of Fort, the security firm in charge of the vaults. “I’m amazed.”

“I’m really feeling a lot of amazement,” he added.

M. Dupont went on to stress that the security of the vaults is “absolutely top class, top notch, top banana, seriously,” and urged people not to panic. Nonetheless, jewel collectors across Europe are expressing grave concern for the safety of their prized possessions, and many are taking steps to move their most valuable jewels to new secret locations.

This is the second incident at the Fort Vaults this fortnight. Three masked robbers attacked the vaults last Wednesday, but were quickly apprehended before they were able to remove anything.

Max looked at the photo of the diamond, which seemed to wink from the page, as if it was pleased to have made its escape. Strange to think that it, too, was travelling to Istanbul. What sort of person, Max wondered, was a diamond thief? She tried imagining that she was a thief, the tiny diamond winking in her pocket while police hunted all over Paris.