The Stuart Sapphire from the Scottish House of Stuart part of the British Crown Jewels is currently at the back of the Imperial State Crown. Originally set in the crown of King Alexander II of Scotland for his coronation in 1214, it was then claimed by Edward I of England in 1296. It then passed through the hands of King Edward III of England, his brother in law King David II of Scotland and his sister Marjorie Bruce whom later named it after her son Robert II first monarch of the House of Stuart.
Oliver Cromwell sold the Stuart Sapphire with the rest of the Crown Jewels but it was returned to Charles II of England once the monarchy had been restored. When James II went into exile in France in 1688 it's believed that he smuggled the sapphire with him and after his death it was passed to his son James Stuart. He in turn passed it on to his son Henry Benedict the Cardinal Duke of York and after his death it was left to George III.
In 1838 Queen Victoria had the Stuart Sapphire set into the front of the Imperial State Crown just below the Black Prince's Ruby. In 1909 it was moved to the back of the crown to make space for the 317 carat (63 gram) cushion-shaped Cullinan II diamond.