The Doctor laughed, long and loud. "Of course humans are trouble!" he chortled. "That's what makes them so wonderfully human! Seriously, though," he said, "you can be responsible for someone without enslaving them. I haven't enslaved anyone, but I still try and look after them."

He put his head on one side and shrugged. "As long as the world is saved," he said with a grin. "I don't mind the reason."