Producer and script editor Matt Fitton said: "After their little trip into the future in Cloud Eight the Doctor and Rose are back to the Powell Estate - once again that mysterious elastic band bringing them back. They find the place in complete turmoil, with loads of historical figures running amok.

"Katherine Armitage is great at creating a really vivid story world, filling it with characters, and finding a high concept idea to spin off on. It's really interesting to look at places around London, places where people live, and think about how much history there is there."

Writer Katherine Armitage explained the idea behind her story: "I was thinking about the idea of history as this very highfalutin thing which belongs in books and dusty libraries. And actually, when you walk around London, one of the things I love is the blue plaques - there’s a nondescript little house, and someone amazing lived there for a while. These people are hiding everywhere.

"And so I had the idea of making them come to life, an estate being overrun by people of the past - but then, obviously, there's got to be something sinister behind them! Pandemonium means where all the devils are...