Permanent-presence watching brief of the construction of a 250mm diameter gravity feed in July 1999 along the Thames Water Boars Hill Main at Harcourt Hill, Oxford. This was carried out by one archaeologist. The topsoil stripping and pipe-trenching process was carefully monitored, and all archaeological remains investigated and recorded. The project yielded nearly sixty sherds of locally made Romano-British pottery, along with several worked flints and sherds of prehistoric and post-Roman pottery. Excavation of the pipe trench revealed two layers of hillwash containing burnt clay and charcoal flecks but no securely datable material.