He was perhaps William, son of the William Dimmock who in 1366 held lands in west Devon at Ermington, Harford, North Ludbrook and Plympton and on whom was settled in 1374 the manor of Little Modbury;
Through marriage to a widow Dimmock acquired property in and near Colyton in the east of the shire; and at the Exeter assizes of July 1394 he and his wife brought an action against Thomas Sutton for disseising them of her dower.
Some time between 1417 and 1424 Dimmock’s daughter-in-law, Agnes, petitioned the chancellor for redress after Sir Hugh Courtenay and Cecily Dimmock (William’s widow) had evicted her from land in Henok Manaton, Little Manaton and Honiton. Cecily died before April 1438.
