The Manor and Castle of Fonmon, near Barry Howard J. Thomas The St John period The manor of Fonmon was one of four fees of Penmark held under the de Umfraville family. It contained 800 acres, most of it good quality arable land, and included the hamlets of Fonmon, East Aberthaw, Burton, and Fontygary. In Despencer's Survey of 1320 the manor was assessed as containing 7 ploughlands.1 According to traditional accounts, Fonmon was given by Robert Fitzhamon in 1091 to Oliver St John (one of his twelve knights) as a reward for assisting him in the conquest of Glamorgan. This account is certainly fictitious as also is that of the earlier generations in the descent from Oliver St John given in several sixteenth- and seventeenth-century pedigrees.2 The St John family are not found in the county before 1200, and the relationship of the Glamorgan line to the older families of St John of Stanton St John (Oxon.) and Langham (Surrey), and St John (or Port) of Basing (Hants.) and Halnaker (Sussex), remains obscure.3 The absence of the St Johns in Glamorgan records before this date is puzzling and may indicate that Fonmon in the twelfth century was held by some other family, or that it had not been sub-enfeoffed by the Umfraville's until the close of the century. It is interesting to note that de Haia and de Cantelupe heiresses, both members of families with Glamorgan and Gwynllwg connections, intermarried early with the Halnaker Basing line.4 If the St Johns of Fonmon are cadets of either of the two St John families, then the split must have occurred before the 1280s. However, it is certain that the St Johns of Fonmon were the same family as that which held the manors of Instow (Devon) and East Luccombe (Somerset).5 The Glamorgan evidence, though scanty, when correlated with the descents of these English manors enable a fairly