Oh yes, of course: end of the epilogue for A Good Day, and the calculations are finished and the Seeker can now safely visit a parallel universe. It didn't occur to me that canon could count as a parallel universe, but why shouldn't it? Makes perfect sense now.

Also, going back and re-reading the epilogue with the Seeker's talk with Clara about his intentions in taking over the universe reverberates in all sorts of interesting ways off of his parent's much madder behaviour in Death in Heaven.

(And, switching threads, love the “Gee, writing is Hard” Darcy icon...)