If you're thinking of Augustine, he was met by local Christians when he arrived in Britain on his mission.
There's plenty of evidence that the church there was functioning from perhaps as early as the 30s AD but at least from first or second century. Three British bishops were in attendance at the Council of Arles in the early 300s.
Elfinspell: 314 A.D., British signers at the Christian church council at Arles from Haddan and Stubbs, English translation by Cheyney, Edward P., Readings in English, History of the Classical Period, Roman Britain, fourth century A.D., primary source, Geography, Exploration, Antiquity,
