This document sets out the results from an archaeological watching brief undertaken during the refurbishment of the West Bailey toilets at Southsea Castle, Portsmouth. The watching brief was carried out on the 25th January 2021 by West Sussex Archaeology Ltd on behalf of Portsmouth City Council. The results revealed two sections of the outer face of the north wall of the Tudor castle, together with stone wall footings and brick sleeper walls associated with two early 19th century casements.