The Doctor considered what Jemma had said about his show getting dark over the years, and asked, "Did it start getting dark after the Time War?" Usually he didn't like discussing that part of his life, but he figured since she'd seen his show, the Time War must've been brought up. He also wondered how much of the Time War she knew about, the horrors he committed.
A lot of running made him laugh. "That I do. Good exercise, though."
Standing by the door, at the top of the ramp, he watched as his new guest looked around, pleased by her reaction. Suddenly, he asked, "What sort of scientist are you?"