The River Tamar forms the South-Eastern border of the County of Cornwall. The Cornish people claim that Cornwall is a separate, Celtic country (named "Kernow" - flag, Black with White Cross) and should have autonomous rule. There is a Cornish Language, v. similar to the language of Brittany, the last native speaker of which died about ninety years ago (? could be more) but there are some attempts to revive it.
English people hold that the Tamar prevents wholesale invasion of England by the Cornish!

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