After the death of William de Londres, the Lord of Glamorgan, his extensive holdings were granted to the powerful Gilbert de Clare in 1217 AD.
The subjugation of Glamorgan, begun by Fitzhamon, was finally completed by the powerful De Clare family, who’s centre of power was the impressive Caerphilly Castle.
At this time, the lowlands of Glamorgan were manorialized, whilst much of the isolated uplands were left under Welsh control, at least until the late 13th century.
With the death of the last Welsh ruler, LLewellyn ap Gryffydd in 1282 AD, Anglo Norman control over the whole country was secured – at least until the time of Owain Glyndwr!.
From the Middle Ages Llangan was bound manorially with Penlline – the old records associate Penlline, Llangan and Goston.
In 1435 Henry VI – bequeathed the Manor of Corntown, of which LLangan, Penllyn and Goston were a part, by virtue of a Royal Charter as follows:-
“To John and Joan Eyer and their heirs, if they failed to produce heirs then to David and Gwenllian Matthews for the terms of their lives and thereafter to their son Thomas Matthews and his male heirs forever. Should there be no such heirs, to the male heirs of David Matthews forever.”
As the Eyers died without heirs – the Manor fell to the Matthew family and hence to George Matthews who died on 14th November 1558. His heir was William Matthews aged 26 years.
Edward Rae held in tenure a parcel of the Manor of Corntown and Edward Carne, Thomas Matthews and Christopher Tuberville held the Manor of Llangan, Penlline and Goston in socage, that is a feudal tenure of land involving payment of rent or other non- military service to a superior.
St Mary Hill Fair was established sometime in this era, it was originally of a religious nature and was held on 15th August, the Feast of the Assumption of the Blessed Virgin Mary.
Later on, the nature and the date of the fair changed it was held on 26th August and became a gypsy fair.
Given the good agricultural land in the area, the Normans established their corn growing manors here, based on the feudal system which was designed to enable a relatively small amount of aristocrats to dominate a large number of peasants. They controlled the law, religion, education, land tenure, coinage, the military and the ownership of weapons.
From the time of the Norman Conquest, roads ran out from Treoes, marking off the open fields from the common land. Moor Mill on Treoes Moors was the corn mill for Penlline, Llangan and Treoes. It is still possible to trace the old road called Heol-y-Millway running from Penlline to Treoes.
Treoes is of great antiquity and is a perfect example of a street or ribbon village dating back to the Middle Ages (David. J. Francis).