Roman client kingdoms in Britain

The Roman client kingdoms in Britain were native tribes who chose to align themselves with the Roman Empire because they saw it as the best option for self-preservation or for protection from other hostile tribes. Alternatively, the Romans created (or enlisted) some client kingdoms when they felt influence without direct rule was desirable.

The beginnings of the system are to be found in Caesar's re-enthroning of Mandubracius as king of the Trinovantes, who had been de-throned by Cassivellaunus and then aided Caesar's second invasion of Britain in 54BC. The system further developed in the following hundred years, particularly under Augustus's influence, so that by the time of the Roman invasion in 43 AD several Roman client kingdoms had become established in the south of Britain.

These were also partially due to the expansion of the Catuvellauni under Cunobelinus in the southeast, and partly as a result of the invasion itself, and included Cogidubnus of the Regnenses, Prasutagus of the Iceni and Cartimandua of the Brigantes and, probably, Boduocus of the Dobunni. The antecedents of the Regnenses, the Atrebates, had (in their Gallic and British forms) been client kingdoms of Rome since Caesar's first invasion in 55 BC.

In the north of Britain, ongoing border struggles across the defensive walls led to the establishment of buffer states, including the Votadini in Northumberland.

...
Wikipedia