Brittonicisms in English are the linguistic effects in English attributed to the historical influence of Brittonic (i.e. British Celtic) speakers as they switched language to English following the Anglo-Saxon settlement of Britain and the establishment of Anglo-Saxon political dominance in Britain. The research into this topic uses a variety of approaches to approximate the Romano-British language spoken in Sub-Roman Britain on the eve of the Anglo-Saxon arrival. Besides the earliest extant Old Welsh texts, Breton is useful for its lack of English influence.