The Tower of London, officially His Majesty's Royal Palace and Fortress of the Tower of London, is a historic castle on the north bank of the River Thames in central London, England. It lies within the London Borough of Tower Hamlets, which is separated from the eastern edge of the square mile of the City of London by the open space known as Tower Hill. It was founded toward the end of 1066 as part of the Norman Conquest. The White Tower, which gives the entire castle its name, was built by William the Conqueror in 1078 and was initially a resented symbol of oppression, inflicted upon London by the new Norman ruling class. The castle was also used as a prison from 1100 until 1952, although that was not its primary purpose. A grand palace early in its history, it served as a royal residence. As a whole, the Tower is a complex of several buildings set within two concentric rings of defensive walls and a moat. There were several phases of expansion, mainly under kings Richard I, Henry III, and Edward I in the 12th and 13th centuries. The general layout established by the late 13th century remains despite later activity on the site.

Richard I, known as Richard Cœur de Lion or Richard the Lionheart because of his reputation as a great military leader and warrior, was King of England from 1189 until his death in 1199. He also ruled as Duke of Normandy, Aquitaine, and Gascony; Lord of Cyprus; Count of Poitiers, Anjou, Maine, and Nantes; and was overlord of Brittany at various times during the same period. He was the third of five sons of Henry II of England and Eleanor of Aquitaine and was therefore not expected to become king, but his two elder brothers predeceased their father.