To quote from my trusty Ladybird book, “Discovering The Tower of London“, “The ravens are certainly the most important residence of the Tower of London, for – as the story goes – if they ever leave, the Tower will fall and England with it. As soon as the castle was built ravens must have flown in to feed off the rubbish from the kitchen and there may have been some at the Tower ever since“.
My souvenir guidebook from the Tower goes further and insists that the ideal number of ravens resident within the fortress is six, thanks to King Charles II. “The King’s Astronomical Observator” or the first Astronomer Royal, John Flamstead, then based at the Tower, appealed to the King to have the ravens, who were taking over the place by this point, removed completely from the fortress; presumably because they were getting in the way of his telescope. King Charles II, understandably weary of doing anything that might course the kingdom to fall, insisted that at least six ravens be present at all times, but the rest could be cleared out. He also gave Flamstead a warrant to set up an observatory in Greenwich, so his telescope would be well out of the way, founding what would become the Royal Observatory, Greenwich, what would become the home of the Greenwich meridian and Greenwich mean time. I wonder if Flamstead had stayed on at the Tower, despite the ravens, we would have ended up with a Tower Hill meridian and Tower Hill mean time?