[6] When Henry was assassinated shortly afterward, Marie became regent for her nine-year-old son Louis XIII, who then exiled her in 1617 due to her mismanagement and ceaseless political intrigues.

Despite her debts piling up, Marie managed to hold on to the Beau Sancy, but the stone eventually had to be sold to pay for her funeral and assorted other expenses.

The Restoration being successful, Mary joined her brother in London, where she died in 1661 without having been able to redeem the Beau Sancy, or return her other jewellery from England.

[6] This task fell to her mother Amalia of Solms-Braunfels, who was able to solve the problem by arranging for her grandson William III to marry James' II daughter Mary, with the pair being crowned joint monarchs of England in the Glorious Revolution of 1688.

[12] Eager to emulate other absolutist monarchs after his self-elevation to the title of King in Prussia just one year earlier, Frederick considered the storied Beau Sancy to be the cornerstone of the Prussian Crown Jewels.

Frederick the Great famously abhored all signifiers of stylishness, and gave the stone to his wife Elisabeth Christine, who had the Beau Sancy reset in the Rococo style as a bouquet jewel.

The Beau Sancy retained its exalted position amongst the crown jewels, but was reset several times as a pendant, which it was customary for the bride to wear at royal weddings.

At the end of the Second World War, it was transferred to a bricked-up crypt for safe-keeping, where it was found by British troops and returned to the estate of the House of Prussia.