Note 113 — Chapter I · THE ENGLAND OF HENRY I. 1100–1135.
Reading edition
The chief stronghold of the new fortress, however, was not on the mound; it was a lofty tower—still standing—on the western side of the enclosure. It was built by the first Robert of Oilly, in 1071; Ann. Osen. ad ann. See Parker, Early Hist. Oxf., pp. 202–204.