Idea vs. Execution

And while you're on the Blink page at the BBC site, I recommend reading the original Steven Moffat Short Story the episode is based on. This is an excellent example of the extent to which an idea is changed and embellished as it goes through the TV episodic writing process. The original idea is still clearly recognizable, but it has been very much adjusted and in this case is sharing the episode with another, even larger idea. (Which illustrates another of my personal writing rules, which is that When You Think You Have Too Much Story, That's When You Have Enough Story. The original Sally Sparrow story by itself, though lovely, would have dragged dully if stretched out to an hour.)