A map showing tribes of Britain in 600AD is almost identical to a new chart showing genetic variability throughout the UK, suggesting that local communities have stayed put for the past 1415 years.

Really interesting article here.

The most striking genetic split can be seen between people living in Cornwall and Devon, where the division lies exactly along the county border. It means that people living on either side of the River Tamar, which separates the two counties, have different DNA.