Is there any evidence of ancient or medieval sources describing Britons as Celts?

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I thought it was the linguistic association which led modern authors to extend the term Celtic from the continental Celts to the islander speakers of other Celtic languages. If neither Britons nor Anglo-Saxons described the Britons as Celts at the time, it's unlikely that this is the root of Chiltern. 173.66.211.53 (talk) 01:25, 31 July 2013 (UTC)Reply