Recent radiocarbon dating
Scientists say big cat skulls found in a moat that protected the fortified palace provide clues to when and how these lions were kept.They also reveal insights into the lives of England's early kings and queens.
As soon as a living organism dies, it stops taking in new carbon.
The ratio of carbon-12 to carbon-14 at the moment of death is the same as every other living thing, but the carbon-14 decays and is not replaced.
Infamous as a place of torture and executions, and home to the British monarch's Crown Jewels, the Tower of London was also one of the world's oldest zoos.
Researchers have been delving into the history of the royal menagerie, using animal remains to reveal the secrets of medieval lions once locked up in the Tower.
Mr Miller sent the sample to the University of Georgia, Center for Applied Isotope Studies, for this purpose.