The correlation between external factors such as age, gender, ethnic group membership and language variation is one of the stalwarts of sociolinguistic theory. The repertoire of individual members of speaker groups, vis-à-vis community-wide variation, represents a somewhat slippery ground for developing and testing models of variation and change and has been researched with reference to accommodation (Bell 1984), style shifting (Rickford, John R. & MacKenzie Price. 2013. Girlz II women: Age-grading, language change and stylistic variation. Journal of Sociolinguistics 17. 143–179) and language change generally (Labov, William. 2001. Principles of linguistic change, vol. 2: Social factors. Oxford: Blackwell). This paper presents and assesses some first quantitative evidence that non-mobile older speakers from Tristan da Cunha, an island in the South Atlantic Ocean, who grew up in an utterly isolated speech community, vary and shift according to external interview parameters (interviewer, topic, place of interview). However, while they respond to the formality of the context, they display variation (both regarding speakers and variables) that is not in line with the constraints attested elsewhere. These findings are assessed with focus on the acquisition of sociolinguistic competence in third-age speakers (particularly style-shifting, Labov, William. 1964. Stages in the acquisition of Standard English. In Roger Shuy, Alva Davis & Robert Hogan (eds.), Social Dialects and Language Learning, 77–104. Champaign: National Council of Teachers of English) and across the life-span generally.