I heard this story once," she said, "where this bloke got locked up for years and years and he learned amazin' stuff about the universe and everythin' from another prisoner who was incredibly clever, and then he escaped and got his revenge." "What incredibly clever stuff do you know about the universe, Gytha Ogg?" said Granny. "Bugger all," said Nanny cheerfully. "Then we'd better bloody well escape right now.