From 1135-1154 Thomas was chancellor. It is uncertain how much of this time he spent at Berkhamsted but during this period extensive building works took place here. 1157-8 he spent money on the King’s houses on the motte and on building a chamber within the bailey. Until 1162 building continued almost yearly.
Building work undoubtedly swallowed up part of the £300 which the King had accused Becket of misappropriating. The castle left Becket’s hands in 1163 after a stormy meeting between the King and Becket, by then Archbishop of Canterbury, at which Henry deprived him of the Honours of Eye and Berkhamsted.