I love that scene. Shame her New Who appearance was totally wasted like it was, but what do I expect from Waltless Disney and the current BBC these days? This article link isn’t about that, though. Back when even the writers didn’t know where the Doctor and Susan came from, William Hartnell (the REAL First Doctor) and Carole Ann Ford came up with their own backstory for where our two time-travellers came from. Since Radio Times has it behind the wall, here’s a posting on it from the “Winter Is Coming blog” from Fansided.
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