The Glass Tower was obviously inspired by a picture of the ‘Gherkin’, otherwise known as 30 St. Mary Axe, one of the most distinct new buildings in London. It was seen shattering in the Doctor Who episode, Christmas Invasion, but was obviously repaired in later episodes.

I transferred the building to a plain of blue grass on a distant planet and peopled it with odd sorts who had obviously lost the plot. The obsession with cleanliness that necessitated ion showers and paper clothes was going to be a bit more central to the storyline than it actually turned out to be. But the illusion of living under siege from a hostile world outside was given higher prominence.

The main purpose of the story was to give Donna and Ben some time without The Doctor around to cement their relationship. Obviously they ARE an item by now. Somebody commented that a lot of my characters go off into the sunset with happy relationships. Well, I don’t think there is any harm in that. Why not? Too many Doctor Who characters have miserable things happening to them. Mine leave The Doctor far better off than they began, and I fully intend that to be the case with these two.

Ultimately, of course, this story is another velvet revolution, with The Doctor bringing the people outside and inside the tower together. It has that much in common with The Savages, way back in the William Hartnell days, and even Face of Evil, where the Tesh and Seveteem realised they had a common ancestry and purpose through The Doctor’s intervention. There were casualties, including the insane leader of the Tower community, Dominic. But mostly it was a happy ending for them all.

http://en.wikipedia.org/wiki/30_St_Mary_Axe
http://www.30stmaryaxe.com/