We all loved Doctor Who's companion Sarah Jane Smith, the plucky reporter who starred in not one but two spinoff series. We particularly loved the late Elisabeth "Lis" Sladen, the actress who brought Sarah Jane to life. But it turns out that she wasn't the first person to have been cast as Sarah Jane.
The role of Sarah Jane was initially given to actress April Walker. According to SFX, Walker went to several rehearsals, but never had the chance to appear on film:
Why was she replaced? Well, the story goes that Pertwee liked his Doctor to be a paternal, protective figure, and felt that his co-star should be young, petite and vulnerable (Sladen's take on this was that Pertwee was the sort of man who "likes to impose themselves physically on smaller women"). Walker - tall and in her early '30s - didn't fit the bill, as far as the star was concerned. And so her contract was cancelled. Producer Barry Letts obviously felt bad about the whole affair, as he later went on to cast Walker in his 1976 production of The Prince And The Pauper.
Walker's identity was recently revealed in the DVD commentary for the episode "Invasion of the Dinosaurs."
SFX writes that Sladen knew the name of the actress she replaced, but never mentioned it because she didn't want to be "unfair" to Walker.
So even though we don't know much about Walker, we're secure in the knowledge that Lis was a class act.