Jack almost interrupted the silence that followed his question with an apology for meddling in the affairs of Time Lords, but the sigh was a prelude to an answer, so Jack stayed silent. He listened and leaned his head on the Doctor's shoulder in return, smelling the man's hairgel.
It struck Jack that the Master was allowing the Doctor to continue his daily hygiene regimen. He didn't know why he should be so surprised by that information, but it made the fire-hose "showers" that the guards gave him every once in a while seem that much worse.
With a sigh of his own, Jack hmmed. "So you two have known each other that long, huh? That's what... over 800 years of back-history?" Jack sat pondering that for a moment, wondering if he and the Doctor would still know each other in 800 years. Then, before the Doctor could answer his first questions, he asked the biggest one he was thinking before he could lose his nerve. "Were you two... involved?"