Vicars' career was very distinguished until 1907 when it was hit by the scandal of the theft of the Irish Crown Jewels. As Registrar of the Order of St Patrick, Vicars had custody of the insignia of the order, also known as the "crown jewels". They were found to be missing on 6 July, and a Crown Jewel Commission under Judge James Johnston Shaw was established in January 1908 to investigate the disappearance. Vicars and his barrister Tim Healy refused to attend the commission's hearings. The commission's findings were published on 25 January 1908 and Vicars was dismissed as Ulster five days later.