200px|Map showing distribution of Brythons in red Prydain (Middle Welsh: Prydein) is the modern Welsh name for Great Britain.
Great Britain and adjacent islands in the 5th century AD, before the invasion and subsequent founding of Anglo-Saxon kingdoms. Prydain (Middle Welsh: Prydein) is the modern Welsh name for Great Britain.
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200px|Map showing distribution of Brythons in red
Great Britain and adjacent islands in the 5th century AD, before the invasion and subsequent founding of Anglo-Saxon kingdoms.