Sark was one of the Channel Islands in the English Channel.
Over several nights in the 1970s, five large circles appeared on a farm belonging to the Oliver family. These were investigated by the Third Doctor and UNIT. After the Doctor translated pictograms, Ikiria descended in her ship. She chose to make contact on the remote island of Sark rather than London so as to avoid causing panic among the general public. (AUDIO: The Rings of Ikiria)