In 1125Ad King Henry I founded the great Abbey of Reading and endowed it with many gifts of land, including the Manor of Thatcham. At the same time Thatcham Hundred ceased to exist, the western part being transferred to Faireress Hundred, and the remainder to the Hundred of Reading. The abbot of Reading was exempted from all taxes and feudal dues in respect of lands granted to him, and he was allowed to hold Manor courts. Henry I also allowed the monks the privilege of holding a market each Sunday in Thatcham church. Some authorities believe that a weekly market existed even earlier than 1125AD.
In 1141AD Thatcham Church previously the property of the Diocese of Salisbury, was granted to Reading Abbey by the Empress Mathilda, who at the same time confirmed her father's gift of the Manor to the Abbey.
