Also known as the Irish Crown Jewels, the Jewels of the Order of St Patrick, are at the heart of a still-unsolved mystery. 

King George III created the Order of St Patrick in 1783, as an equivalent order to England’s Order of the Garter and Scotland’s Order of the Thistle. 

The Grand Master’s regalia were stolen from Dublin Castle sometime in late June or early July 1907. The Diamond Star and Diamond Badge were created by jeweller Rundell & Bridge in 1831 when King William IV restructured the order. 

Combined the items had nearly four hundred gemstones. The badge featured blue enamel, emeralds, rubies, and both white and pink diamonds. The star included Brazilian diamonds of the first water, emeralds, and rubies. 

The jewels were last noted to be in their safe on 11 June 1907. It was not until 6 July when they were noticed to be missing- King Edward VII and Queen Alexandra were visiting in the coming days, and the order investiture was then cancelled. 

Five of the collars worn by the knights of the order were also stolen. 

The theft remains a mystery, as the Dublin Metropolitan Police were never able to locate the thieves. While there were several contemporary theories, none were ever substantiated and the jewels remain lost forever.