User:SOTO/Forum Archive/The Reference Desk/@comment-72.241.208.125-20130313210047/@comment-188432-20130314003638

It comes from Human Nature. It's not a reuse of film from elsewhere; it was shot for this episode. You'll note that Tim actually appears in the modern environment shared by the modern Martha, and modern Martha's lines fit precisely into those of Martha-in-the-past. Also, Martha is wearing the all black outfit from the top and tails of this episode — something I'm pretty sure wasn't seen in any previously-produced episode. (But the clinching evidence is that Tim is in the modern environment.)

It's definitely not reuse of footage from other episodes.