The Crown Jewels of Ireland were heavily jewelled insignia of the Most Illustrious Order of St Patrick. They were worn by the sovereign at the installation of knights of that order, the Irish equivalent of the English Order of the Garter and the Scottish Order of the Thistle. Their theft from Dublin Castle in 1907 remains unsolved.

History:

King George III instituted the Order of St Patrick in 1783. Among the insignia of a knight were a star and a badge; in the royal set of the insignia these were composed of rubies, emeralds and Brazilian diamonds.

Theft:

In 1903, the jewels were transferred to a safe, which was to be placed in the newly constructed strongroom. The new safe was too large for the doorway to the strongroom, and Arthur Vicars, the Officer of Arms of Dublin Castle, instead stored the jewels in his office. Seven latch keys to the door of the Office of Arms were held by Vicars and his staff, and two keys to the safe containing the insignia were both in the custody of Vicars.

Vicars was known to regularly get drunk on overnight duty and he once awoke to find the jewels around his neck. It is not known whether or not this was a prank or a practice of the actual theft.

The jewels were discovered missing on 6 July 1907, four days before the state visit of King Edward VII and Queen Alexandra. The theft is reported to have angered the King, but the visit went ahead.

Vicars refused to resign his position, and similarly refused to appear at a Viceregal Commission into the theft (the commission did not possess powers to subpoena witnesses) held from 10 January 1908. Vicars argued for a public royal inquiry in lieu of the commission, and publicly accused his second in command, Francis Shackleton, of the theft. (Francis was the brother of the explorer Ernest Shackleton.) Shackleton was exonerated in the commission's report, and Vicars was found to have "not exercised due vigilance or proper care as the custodian of the regalia." Arthur Vicars was shot dead by the IRA on 14 April 1921.

The Adventure of the Bruce-Partington Plans:

While the official authorities never solved the real mystery it was left to Sir Arthur Conan Doyle to have a variant on the story solved by Great Britain's greatest detective. In 1908 Conan Doyle wrote The Adventure of the Bruce-Partington Plans for The Strand Magazine. Changing the stolen item from the royal jewels to plans for a revolutionary submarine in the British Navy, the author has Sherlock Holmes and Dr. Watson set up a trap that catches the criminal, one "Col. Valentine Walters," who is the brother of a high-ranking, respected official. Walters is apparently based (in part) on Francis Shackleton, whose brother was a prominent public hero. Unlike the real life perpetrators of the theft of the Crown Jewels Walters goes to prison, but dies there shortly after his sentence begins.

The Patricius Enigma:

A further fictional account of the theft of the jewels was published in 2010 by Sean Marshall entitled The Patricius Enigma. As a plot construct in the story the protagonists reveal not only who stole the jewels but also where they ended up.

Additional reading:

Francis Bamford & Viola Bankes, Vicious Circle: The Case of The Missing Irish Crown Jewels (New York: Horizon Press, 1967), 212p., illus.
Tim Coates (ed.), The Theft of the Irish Crown Jewels (Tim Coates, 2003) ISBN 978-1843810070
Marshall, Sean. (2010). The Patricius Enigma. ISBN 978-1453804704.