Built in the 12th century, the site has been of religious interest for much longer. In the 6th century, land was given to Teilo, Bishop of Llandaff (or one of his followers) for a Christian cell. Pertholey translates as 'Defiled Entrance', possibly a reference to early Christian martyrs.

Living Churchyard Project

Encouraged and supported by the Gwent Wildlife Trust, Llantilio Pertholey Community Council and Monmouthshire County Council, St Teilo's has recently embarked upon this project. It aims to develop the churchyard and its boundary features, as places in which wildflowers, trees, insects, birds and other animals can flourish. Information and interpretation boards have been placed in the Churchyard to help our understanding of nature and habitats, and there interactions with the environment.

There are social aims too, involving both the local community and the Church Primary School. Children have grown pots of wildflowers from seeds, and have planted them in the wildlife areas. They also visit the project for ecological studies.

The most recent development has been along the riverside, where the Gavenny river forms the southwest boundary of the churchyard. An all-weather path allows access (including wheelchairs) to view the riverside wildlife (especially birds and insects), and to hear the sounds of running water through the small rapids and falls. Benches are placed at interesting points along the path.

A simple memorial garden in the shape of a Celtic cross has been developed, as a place for quiet contemplation, reflection and remembrance of those who have been laid to rest in the churchyard.