For 300 years (between 600 and 900), having annexed or gained submissions from five of the other six kingdoms of the Heptarchy (East Anglia, Essex, Kent, Sussex and Wessex), Mercia dominated England south of the River Humber: this period is known as the Mercian Supremacy.
Durante 300 anos (entre o 600 e o 900), logo de anexar ou adquirir a submisión de cinco dos seis reinos da heptarquía (East Anglia, Essex, Kent, Sussex e Wessex), Mercia dominaba Inglaterra ao sur do río Humber, este período coñécese como a supremacía merciana.