Cornwall Archaeological Unit (CAU) undertook a programme of archaeological monitoring during the groundworks ahead of installation of a ground source heating system at Trelissick House, Feock, Cornwall, NGR SW 83670 39515. A total of 35 features were identified of which 25 were cut features, and 10 were built structures. Unstable ground conditions, and the narrowness of the trench sections, made access difficult or impossible. Additionally, there was significant variation in the depth and character of deposits across the site, with often complex relationships and stratigraphy. It was clear that several phases of considerable landscaping had been carried out across the site over time. Significant features identified include ditches, pits and postholes associated with settlement activity to the south of Trelissick Home Farm. Pottery from one of the ditches and one of the pits was of Roman-period date, specifically Romano-Cornish gabbroic pottery types dating from the 2nd Century AD but in use up until the 5th Century AD. Pottery from another ditch, and from one of the postholes, was medieval Lostwithiel Type wares, dating from the 13th Century AD. Part of a post-medieval system of stone-built drains was uncovered below several made ground deposits. Part of a concrete pad and tarmac areas were also identified, which potentially date to the occupation of Trelissick House by a United States anti-aircraft battalion in 1944, as part of the run-up and preparations for D-Day. Recommendations for mitigation ahead of any future work would include further geophysical survey, targeted evaluation and/or open area excavation. The discovery of the Romano-Cornish wares within features at Trelissick potentially extend the origins of settlement here back to at least the 2nd Century AD, illustrating a direct association between the early medieval Tre settlement and the earlier Roman-period settlement. This association suggests that Cornish Tre settlements are very likely to stem from much earlier roots, the Tre name denoting the time from when these settlements were first named and documented. The discovery of Lostwithiel Type ware within features at Trelissick potentially indicates the site of settlement dating from the 13th century onwards. The proximity of features of Roman-period and medieval date at Trelissick indicate the likely focus of medieval and earlier settlement at Trelissick was probably to the south of, and potentially underlying, Trelissick Home Farm.