A small side tower with a pointed turret, and crypt chapel at its base and another chapel above, was built on the south-east side of the early east end by Prior Conrad in 1108 as part of Archbishop Anselm's improvements to the cathedral. The crypt chapel was dedicated to St. Gabriel, whist the upper chapel was dedicated to St. Peter and St. Paul. Anselm, however, was not to see his new church building consecrated, as he died in 1109. He was buried in the chord of the apse of the chapel of St. Peter and St. Paul, which later became named St. Anselm's Chapel, and the tower also became St. Anselm's Tower.

Between 1153 and 1167 Prior Wibert strengthened the tower and chapel and added a wall fresco of Paul picking up the viper. In the 14th century, 1336, a large decorated window was added.

Hasted, E, 1799, The History of the Ancient and Metropolitical City of Canterbury. Vol 1. Canterbury (Article in monograph). SKE29735.

Willis, R., 1868, 'The Architectural History of the Conventual Buildings of the Monastery of Christchurch in Canterbury' (Article in serial). SKE30206.

Collinson, P., Ramsey, N. & Sparks, M., 1995, A History of Canterbury Cathedral (Monograph). SKE30201.