Known as the 'First Star of Africa', Cullinan I is the largest colourless cut diamond in the world.  In 1911 the Crown Jeweller, Garrard, mounted it in the Sovereign's Sceptre which had been made for Charles II's coronation in 1661.  The diamond is so large that the sceptre had to be reinforced to take its weight.  Nevertheless, the structure which holds the diamond is hinged, so the stone can be removed and worn separately if desired.