Pure Earth brought together several ideas that I wanted to use and which would not stand alone as a theme.

First, I wanted to use the idea of The Doctor running from a ball of fire along a passage that we saw way back in the original 2005 trailers. That was never a part of any TV episode but seemed too good to waste. So it became part of the quest by The Doctor and the twins to find a source of energy for their Chinese TARDIS.

Second, the idea of a BNP like movement in the 23rd century that didn’t like aliens. This would be especially interesting if compared with Rose’s 21st century experiences of dating Mickey. Racism becoming speciesism two hundred years later.

Third, an adventure in which Michael the butler would feature. He was first introduced in the penultimate episode of Unfinished Business when he got bashed on the head by the people who kidnapped The Doctor. In the first of the New Lords of Time stories he is on the periphery, talking to The Doctor about Rose’s efforts to do housework while pregnant. This time he had a more heroic role. Michael will feature in future stories, but a lot of the time he WILL be peripheral.

One thing that changed in this story from the first draft was the extent of the casualties among the Pure Earthers. Originally, one of the twins was going to send one of the terrorists crashing through the window, killing him. But the twins are still not eighteen and the idea of one of them killing with their bare hands at that age did not sit well. Nor did the family going off for dinner afterwards in that case.