The origins of the ceremony are unknown. It may have begun during the Middle Ages, and it is often stated that a ceremony in some form has been held since the 14th century. Written instructions that the keys should be placed in a safe place by a Tower officer, after securing the gates, date back to the 16th century. In its current form the ceremony is likely to date to the 19th century when the institution of the Yeomen Warders was reformed by the then Constable of the Tower, the Duke of Wellington.