Slavery actually formed an important part of the early medieval English economy throughout the Anglo-Saxon period and post-Conquest, before tapering off in the twelfth century. Anglo-Saxon legal codes, especially those concerned with weregeld, reference slaves throughout, and Domesday Book, for example, often lists the number of slaves in a settlement.

The decline is in part due to changing social views on the acceptability of owning people (prominent authors such as William of Malmesbury condemn slavery as a 'wretched institution'), and partly because of the ever-expanding borders of Christendom. It's explicitly forbidden for a Christian to own another Christian as a slave, and as the Church expanded throughout the early medieval period, so the pool of territories from which slaves could be taken grew ever smaller.