The oldest judicial procedure in England, dating to the 12th century, is the annual Trial of the Pyx. This is a formal legal procedure during which the Assay Office tests over 50,000 coins taken at random to check that their metallic content is within the boundaries set by law.

The testing begins in February each year and lasts for two or three months. When the testing has been completed, the Trial of the Pyx is held, wherein the verdict as to the content of the coins is announced before a jury including members of the Goldsmiths’ Company and the Queen’s Remembrancer (who is also the senior judge of the Royal Courts of Justice).

The Chancellor of the Exchequer attends the trial for, as chancellor and custodian of the royal exchequer, the chancellor has responsibility for the purity of the coinage of the realm. Strictly speaking, should any coins fail at assay, then the chancellor would be liable to execution but luckily for recent chancellors the coinage has proved true.