“What if I said that’s the future you?” the Doctor asked.
Jack tilted his head speculatively. “Well then, I’d say I look damn good for five billion years old. Nice to know I’ll always have a face that stands out in a crowd. And I bet after all that living there can’t be anyone with more knowledge and... experience than me. In fact, maybe I should go and say hello.”
“Jack,” the Doctor chastised.
“Tell me you wouldn’t do the same, given the chance.”
“Oi, I run into myself all the time without doing... that.”
Jack laughed. “Your loss.”
“Yep, that’s me,” Jack said. “And just imagine what I could be like by the time I’m him.”
The Doctor suddenly realised he might have made a big mistake.
It would be a miracle if the universe survived the cataclysm of two Jack Harknesses being in the same room.