Kingdom of England
Before the Romans arrived, what is now considered to be modern Britain consisted of around twenty two tribes. Following the collapse of the Roman Empire in Britain, seven tribes or kingdoms existed until in 827, Northumbria submitted to Egbert of Wessex at Dore, briefly making Egbert the first king to reign over a united England. It ended on 1 May 1707 with the Acts of Union 1707, which added Scotland to the Kingdom to form the Kingdom of Great Britain.