"Oh! That. That... was part of the punishment. Time Lords have this way of cheating death, we call it regeneration. Every cell in our body renews itself. But it means that physically we look different, sound different, have different tastes. As part of my punishment, they forced me to regenerate."

He'll just skip over the part that it's happened eleven or so times since they last met. He pulls a sceptical expression. He wants Jamie to believe him, but he isn't sure the lad will.