Well, fantastic as meeting a slayer might actually be, if she was simply going to pummel potential informants into a pulp, this would be very frustrating.
"Oh, fine, fine," he said, exagerrating the niceness of the words. "It's just... he doesn't belong her. And he might've shown up round the time everybody else went missing. You ever seen one of him before?"
"HEY," the demon/alien protested.
"One moment, if you please," the Doctor said, turning his attention back to Faith. "I'd like to know how he got here. And if he's violent. And if he lies, is unhelpful, or turns out to be a right bastard, by all means, feel free to beat 'em up."
"HEYYYYYYYYYY!" the demon/alien said louder.
The Doctor sighed.
"You could wait your turn, y'know," he said, turning toward it, sonic screw driver still in hand. "When did you get here, and how?"