"Yes, of course I've killed Jack a lot," the Master replied, not getting the signal not to talk about it. Or perhaps getting it and talking about it anyway, because an opportunity to make the Doctor cringe a bit was too instinctive to ignore. "Doesn't mean I wouldn't be interested in him under different circumstances too. He's a fascinating man, even without the immortality thing."
He stepped into the lift as it arrived and glanced back at the Doctor. "I wonder how different Miss Tyler is as a man. That sounds intriguing."