I was flabbergasted to be asked to write an episode - partly because I’ve been so absorbed in the last few series that I’d sort of forgotten that it wasn’t real.

There are more stars than there are people. Billions, Alan had said, and millions of them might have planets just as good as ours. Ever since I can remember, I’ve felt too big. But now I felt small. Too small. Too small to count. Every star is massive, but there are so many of them. How could anyone care about one star when there were so many spare? And what if stars were small? What if all the stars were just pixels? And earth was less than a pixel? What does that make us? And what does that make me? Not even dust. I felt tiny. For the first time in my life I felt too small.

I was flabbergasted to be asked to write an episode - partly because I’ve been so absorbed in the last few series that I’d sort of forgotten that it wasn’t real.