British Sign Language

British Sign Language, or BSL, is a language found in the United Kingdom. It is one of three sign languages spoken natively within the country. A majority of speakers are deaf or hard of hearing, but many others within the BSL-speaking community are hearing, all of whom make up the Deaf community.

In 2119, Cass, the second in command for an underwater mining facility in Scotland, communicated with her team only in BSL, which was interpreted to and from 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)

Behind the scenes
British Sign Language was used on-screen by a character for the first time by Sophie Stone, who played Cass in Under the Lake.