 However, after learning of a reference to a psalter owned by Becket in a sacrists' roll from Canterbury Cathedral, de Hamel realised that the library's psalter matched the one described in the sacrists' roll.The identity of the psalter was supported by a 13th-century stained glass portrait of Becket in Canterbury Cathedral in which he cradles a similarly bound and coloured book under his left arm.Based on the workmanship of the psalter, de Hamel guesses that it was originally created for an archbishop, possibly Ælfheah of Canterbury.