The Crown Jewels have been kept at the Tower of London since Henry III’s reign in 1216-1272.
The White Tower was built as the major Norman castle in London, as a locally resented display of Norman power. The Tower of London would have a political position as the symbol of royal rights for centuries to come. William the Conqueror established it just inside the eastern edge of the Roman town walls of Londinium.
The Tower of London has a reputation as a dismal prison, notable for torture and executions … but it actually wasn’t as bad as 16th-century religious propagandists and 19th-century romantic writers made it out to be. The White Tower was only used as a consistent residence for the first century of its existence and was used as a prison early on.
Bishop Randulf Flambard was the first known prisoner, held at the Tower of London by 1100. It wasn’t harsh imprisonment though, he was allowed servants and the wherewithal to throw banquets–possibly not a good thing, considering he made his escape from the tower during one such event.