In 2119, Cass, the second in command on the Drum, an underwater mining facility in Scotland, communicated with her team only in British Sign Language, which was translated by fellow employee Tim Lunn. The Twelfth Doctor attempted to respond to her in BSL, but soon realised he had forgotten how to, apparently having deleted it in favour of semaphore. (TV: Under the Lake) Previously, the Seventh Doctor stated that he knew sign language. (PROSE: Sleepy)
Behind the scenes Edit
Zaqi Ismail, who played her translator Tim Lunn, knew sign language because his sister was deaf. The two had to create several new words in sign language for more science fiction and story-specific terms.
Jean St. Clair, the BSL monitor, helped Stone and Ismail with their signing, ensuring it would be clear and accurate for the audience.
One Doctor Who fan, Elizabeth Harvey, age 14, wrote to Doctor Who Magazine about her delight in seeing BSL and deaf signers represented in Doctor Who, in a letter featured in DWM 493. According to her, though, a deaf person should always have two interpreters accompanying them, in case of sickness, or, in this instance, "death followed by ghostliness".