Thanks, Carol, for bringing back distant memories of punting on the Cherwell and rowing on the Isis. Oh, my misspent youth! Does the aroma of roasting coffee at Carwardine's still waft up Cornmarket to the Broad? That cured me of Nescafé for life.
Anyway, this particular twixt-the-rivers was, specifically, Ctesiphon, where he was killed in action in 1915. The editors of Burke's Landed Gentry evidently didn't believe there was such a place and "corrected" it to Cresiphon. Perhaps that should be a lesson to us, as you say, not to assume everything that looks wrong is necessarily bonkers -- though in the case of Ancestry it usually is.
And I promise never to confuse my alma mater or its home city with any other place, be it in Akron, Ohio, or anywhere else in the world.