The Doctor nodded. He was trying not to admit to himself that the idea of committing to such a relationship terrified him, but a lot of that was because if he was to undertake such a thing it would be with the Master and that would be a very different kettle of fish.
And John was just talking Jamie taking a Master's opinion on punishment. He said, "Just don't let the Master get Jamie carried away on the punishment side of things, eh?"