In the middle of modern London stands the grand eleventh-century castle built by William the Conqueror called the Tower of London. It’s best known as a secure home for the crown jewels or as an ancient prison for those who incurred the king’s wrath. But treasures and traitors weren’t the only things locked behind those fifteen-foot thick stone walls. For about 600 years the Tower was home to the royal menagerie: Lions, tigers, bears, kangaroos, and many other animals lived there.

Kings and queens have been giving each other exotic animals for ages.  After all, what better way to make an impression than to send someone an elephant? These animal gifts began arriving in England in the eleventh century. But unlike the gift of flowers, the animals couldn’t just be admired for a time and then discarded: They had to be housed and fed. The inescapable castle seemed like the…