"Oh, hey, Jack." The Doctor waved absently, focused on the console. Three seconds passed, then his eyes widened and he turned on his heels to face Jack. "I mean. Look, it's... I was trying something. You know the drums he always goes on about? I tried to find what causes them, in his mind, and... I must have hit a reset button or something." He bit his lip, trying to think of how to explain this. "He can't remember anything pf the last... Well, lots of years. He's still before his first regeneration, the way his memories work right now."

He ran a hand through his hair, clearly frustrated. "Captain Jack Harkness, meet Koschei. He just graduated top of his class from the Academy, we're all very proud."