 Then after John died, William held the barony, and after some time ruled the county as William "vicecomes".He, mindful of the welfare of his brother's soul, fulfilled his promise and founded the abbey of St Mary of Sibton, granting his lands at Sibton and his charter of confirmation dated 1149.Sibton Abbey of the Blessed Virgin Mary was founded with the normal complement of 13 monks, but by the thirteenth century the numbers of monks and lay brothers had grown, and the Abbey had grown rich, owning lands across southeast England, including twelve relatively small granges in Norfolk, Suffolk and on the borders of Cambridgeshire, as well as possessions within 10 parishes of the city of Norwich.