The Norman conquest of England began in 1066 AD with the invasion of the Kingdom of England by the troops of William, Duke of Normandy ("William the Conqueror"), and his victory at the Battle of Hastings. This resulted in Norman control of England, which was firmly established during the next few years.
--Wikipedia
A number of scholars argue that the unknown Pictish language was Brythonic, but in Sub-Roman Britain the Picts were distinguished as a separate group, as were the Gaels of Dál Riata. Therefore, the term "Briton" traditionally refers to the inhabitants of ancient Britain excluding the Picts, because many Pictish cultural traits (for example their sculpture, pottery and monuments) differ from those of the Britons and because ancient writers clearly distinguish the two peoples.
--Wikipedia