The Roman client kingdoms in Britain were native tribes which 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. Client kingdoms were ruled by client kings. In Latin these kings were referred to as rex sociusque et amicus, which translates to "king, ally, and friend". The type of relationships between client kingdoms and Rome was reliant on the individual circumstances in each kingdom.
The beginnings of the system are to be found in Caesar's re-enthroning of Mandubracius as king of the Trinovantes, who had been dethroned by Cassivellaunus and then aided Caesar's second invasion of Britain in 54 BC. 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. Client kingdoms were annexed when Rome needed to reaffirm their power in Britain or when the client kings could not manage the kingdoms and surrounding areas any more.
