It was a well known fact that Elisabeth Sladen wasn’t the first actress cast to play Sarah Jane Smith in “Doctor Who” but then producer Barry Letts had always kept secret the identity of the actress originally cast for that role. The few others who knew the secret respected Barry Letts’ will but after nearly forty years that’s been revealed in the production notes of the DVD “Invasion of the Dinosaurs” published this week in region 2 countries within the box “UNIT Files” available on Amazon UK.

Barry Letts passed away in 2009 but there are still memos from that time that reveal that the actress originally cast as Sarah Jane Smith was April Walker. In fact it seems that she was paid for the entire season as she had signed a regular contract.

In 1973 Barry Letts was looking for an actress to play the new Third Doctor’s companion who’d replace Jo Grant alongside actor Jon Pertwee. Apparently, even before starting the production of the first adventure it became clear that there wasn’t the right chemistry between the two of them though they had worked together on stage five years earlier.

Jon Pertwee preferred to have at his side companions he could be protective with, in fact the relationship between the Doctor and Jo Grant was in some ways a father-daughter relationship. Sarah Jane Smith was created as a strong character and maybe that’s why producer Barry Letts had cast a tall actress but Jon Pertwee preferred to a physically petite actress at his side.

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In show business a second choice is simply a better choice to play the role and Elisabeth Sladen turned out wonderful in the role of Sarah Jane Smith. It’s a situation similar to the one that occurred some years before in another legendary British series, “The Avengers“, in which Diana Rigg was the second choice to play Emma Peel.

April Walker was replaced not because of her inability but because she didn’t work in that role next to the star of the show so out of respect for her Barry Letts decided not to reveal her name.

April Walker had her career with roles in many television series but we’ll never know what Sarah Jane Smith played by her would’ve been like.