His
That's the trouble with regeneration. You never know what you're going to get.
But once he got over the shock of the changed appearance, and the post-regenerative trauma, of course, it was quite interesting to see how he’d react to things.
His whole outlook on life would change. He’d see everything differently.
Especially people, he’d noticed. Take Tegan, for example. He couldn’t help but think that his previous regeneration would have had rather less trouble getting her back to Heathrow at the right time. To him, she’d just been a noisy Australian air hostess who’d happened to wander into the TARDIS at a very bad time.
But now… well, she was still a noisy Australian air hostess who’d happened to wander into the TARDIS at a very bad time, but she was his noisy Australian air hostess who’d happened to wander into the TARDIS at the wrong time (he’d introduce her as such, but he thought she might get angry).
It seemed a little strange to be thinking of her as his. Because after all, he’d seem Romana as his, in some way, and others before her.
It was something about this regeneration. He was seeing people differently, and there was something different about the way he saw Tegan.
He was sure he’d work out what it was soon.