Doctor Who has never been one to shy away from a real-life mystery. After all, anyone who's seen The Chase will know that the crew of the Mary Celeste disappeared after the Daleks landed on it while chasing the Doctor through time and space. So this week it's tackling the real fate of the Ninth Roman Legion, which mysteriously disappeared and is thought to have been defeated by Celtic tribes in the north of Britain. The Eaters of Light is also a particularly notable episode because of it's writer Rona Munro - the first person to write for both the modern and classic iterations of the show, having previously written the show's "final" episode Survival in 1986.