A group of ravens is referred to as a congress or an unkindness. The most famous unkindness of six ravens at the Tower of London are employees, kept on staff at the expense of the British government. There are claims that the ravens were decreed to be kept by King Charles II to prevent disaster, or that they had been placed near the Tower in order to dramatize execution proceedings. These days they’re kept around for tourists, and they are fed well (for ravens) on a diet consisting of raw meat, bird formula biscuits soaked in blood, whole rabbit, eggs once a week, and occasional pieces of fried bread.
Ravens are fairly vicious by nature, so the Tower’s Ravenmaster must bond with them over a period of six weeks when they are fledglings. These birds are so vital to the Tower’s image that several fledglings are kept as understudies for the six working birds as they die, even though the average raven lifespan is twenty-five years. The current raven roster at the Tower consists of Gwylum, Thor, Hugin, Munin, Branwen, Bran, Gundulf, Baldrick, Fleur, and Colin.
Update: The legend is that the decree from King Charles II stemmed from the prophecy that if the ravens are removed from the tower, the monarchy will fall. It is believed that John Flamsteed, who was a prominent astronomical observer, complained to the king that ravens were getting in the way of his observations at the Royal Observatory, which was located in the northeastern section of the White Tower. King Charles’ solution to the complaint was to order all of the ravens killed. It was then that a mysterious oracle informed the king that if the ravens left the Tower of London, the White Tower would topple and the whole of England would be plagued by disaster. Superstitious, King Charles ordered that at least six ravens should be kept at the Tower at all times, and he moved the Observatory to Greenwich. It’s rumored that this decree still stands today.