Extremely isolated communities offer 'laboratory conditions' for examining the processes of language change and dialect formation. This book presents findings of the first-ever ethnographic fieldwork on the most remote island in the world with a permanent population, Tristan da Cunha. It documents the historical formation of a unique local dialect and investigates the sociolinguistic mechanisms that underlie dialect contact and new-dialect formation. It also uncovers the linguistic consequences of post-insularity - language change processes as a result of increasing contacts with other communities and speakers. Researchers and students of language variation will find this book a unique resource.