Summary: A lot of things are different in the future.
“He looks familiar,” Martha said, studying a portrait of an elderly man with a receding hairline.
“He should; that’s His Royal Highness King William of England.”
“King? He’s only a prince in my time. But what’s his portrait doing here of all places?” Martha and the Doctor were on an alien world, far from earth.
“Holiday home,” the Doctor said. “Like Balmoral, but a bit further away. The Royal Family comes here every summer. It was William’s idea. The whole moon was gifted to him and his descendents after he helped an alien princess regain her birthright.”