Tower of London. Edward V's uncle Richard, Duke of Gloucester was declared Lord Protector while the prince was too young to rule. Traditional accounts have held that the 12-year-old Edward was confined to the Tower of London along with his younger brother Richard. The Duke of Gloucester was proclaimed King Richard III in June. The princes were last seen in public in June 1483; it has traditionally been thought that the most likely reason for their disappearance is that they were murdered late in the summer of 1483. Bones thought to belong to them were discovered in 1674 when the 12th-century forebuilding at the entrance to the White Tower was demolished; however, the reputed level at which the bones were found () would put the bones at a depth similar to that of the Roman graveyard found, in 2011, underneath the Minories a few hundred yards to the north. Opposition to Richard escalated until he was defeated at the Battle of Bosworth Field in 1485 by the Lancastrian Henry Tudor, who ascended to the throne as Henry VII. As king, Henry VII built a tower for a library next to the King's Tower. Changing use The beginning of the Tudor period marked the start of the decline of the Tower of London's use as a royal residence. As 16th-century chronicler Raphael Holinshed said the Tower became used more as "an armouries and house of munition, and thereunto a place for the safekeeping of offenders than a palace roiall for a king or queen to sojourne in". Henry VII visited the Tower on fourteen occasions between 1485 and 1500, usually staying for less than a week at a time. The Yeoman Warders have been the Royal Bodyguard since at least 1509. In 1517 the Tower fired its cannon at City crowds engaged in the xenophobic Evil May Day riots, in which the properties of foreign residents were ransacked. It is not thought that any rioters were hurt by the gunfire, which was probably meant to merely intimidate the mob. During the reign of Henry VIII, the Tower was assessed as needing considerable work on its defences. In 1532, Thomas Cromwell spent £3,593 on repairs and imported nearly 3,000 tons of Caen stone for the work. Even so, this was not sufficient to bring the castle up to the standard of contemporary military fortifications which were designed to withstand powerful artillery. Although