Construction of the Tower of London began under the rule of which king of England?

The Tower of London is a 900-year-old castle and fortress in central London that is notable for housing the crown jewels and for holding many famous and infamous prisoners.

William I (c. 1028 – 9 September 1087), usually known as William the Conqueror and sometimes William the Bastard, was the first Norman King of England, reigning from 1066 until his death in 1087. His hold was secure on Normandy by 1060, following a long struggle to establish his throne, and he launched the Norman conquest of England six years later. William I created the first fortifications after the conquest of London in A.D. 1066. The Norman invader lacked support among the people of the city and he feared its inhabitants could throw him out. There were several phases of expansion, mainly under kings Richard I, Henry III, and Edward I in the 12th and 13th centuries.

The Tower of London has played a prominent role in English history. It was besieged several times, and controlling it has been important to controlling the country. The Tower has served variously as an armoury, a treasury, a menagerie, the home of the Royal Mint, a public record office, and the home of the Crown Jewels of England.

The peak period of the castle's use as a prison was the 16th and 17th centuries, when many figures who had fallen into disgrace, such as Elizabeth I before she became queen, Sir Walter Raleigh, and Elizabeth Throckmorton, were held within its walls. This use has led to the phrase "sent to the Tower".