Clara and The Doctor in “The Rings of Akhaten”

Still hungry? Well, I brought something for you. This. The most important leaf in human history. The most important leaf in human history! It's full of stories. Full of history. And full of a future that never got lived. Days that should have been and never were. Passed on to me. This leaf isn't just the past, it's a whole future that never happened. There are billions and millions of unlived days for every day we live — an infinity. All the days that never came. And these are all my mum's.

Well? Come on then. Eat up! Are you full? I expect so. Because there's quite a difference, isn't there, between what was and what should have been? There's an awful lot of one, but there's an infinity of the other! And infinity is too much. Even for your appetite.