"..we've solved another riddle. The mystery of Agatha Christie.. tomorrow morning, her car gets found by the side of a lake. A few days later she turns up in a hotel in Harrogate with no idea of what just happened. No-one'll ever know.. [she] married again, saw the world, wrote and wrote.. Thing is, I don't think she ever quite forgot.. where is it? Here we go.. Somewhere in the back of her mind, it all lingered.. Look at the copyright page [passing Donna a copy of Death in the Clouds, "Facsimile edition, published in the year 5 billion!"]. People never stop reading them. She is the best selling novelist of all time. Well, no-one knows how they're going to be remembered.. Same thing keeps me travelling. Onwards?"
- The Doctor, The Unicorn and the Wasp (17/5/2008)