I think lobf's point is that the Britons had absolutely no impact on the rest of the world until the Romans conquered Britain. I wouldn't argue for their removal, though - how much impact did the Sarmatians or Lusitanians have, after all? EB is a game of "what if".
Evidence from burning down and building new hill forts (Almondbury, Sutton Bank/Roulston Scar) by the way, suggest that the Brigantes and Parisi may have been around since c.400 BC. In the South of England, things seem to have been in more of a state of flux.
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