Thatcham prospered greatly under the patronage of the Abbots of Reading, most of whom were very powerful and exercised great influence at court. This influence is manifested in many royal charters concerning Thatcham issued during the twelfth and early thirteenth centuries.
During his reign King Henry II issued three charters confirming the weekly market, and compelling the men of Berkshire to attend Thatcham Market or suffer a fine in default. When the men of Newbury jealous of the privilege enjoyed by Thatcham attacked Thatcham market, overturning stalls and scattering merchandise. King Henry II immediately issued an order forbidding the men of Newbury to injure or interfere with the market. The close proximity of the two markets of Thatcham and Newbury intensified commercial rivalry and much ill fooling existed between them, at least until the reign of Queen Elizabeth I.
In 1218AD King Henry III ordered the Market day to be changed from Sunday to Thursday and in 1222AD the status of Thatcham was further enhanced when the King granted the town a fair, to be held annually on the eve and day of the feast of St. Thomas the Martyr (the 6th and 7th of July). Later this fair was abandoned and two one-day fairs were held instead during April and September lasting until 1888AD.
