 The older view of prehistorians was that the Celtic influence in the British Isles was the result of successive invasions from the European continent by diverse Celtic-speaking peoples over the course of several centuries, accounting for the P-Celtic vs. Q-Celtic isogloss.This view has been challenged by the hypothesis that the Celtic languages of the British Isles form a phylogenetic Insular Celtic dialect group.In the 19th and 20th centuries, scholars commonly dated the "arrival" of Celtic culture in Britain (via an invasion model) to the 6th century BC, corresponding to archaeological evidence of Hallstatt influence and the appearance of chariot burials in what is now England.