Long Newnton was transferred from Wiltshire in 1930. Holy Trinity Church was a possession of Malmesbury Abbey until the Dissolution. The only medieval part is the Late Perpendicular style West tower of three stages, with diagonal buttresses, battlements and pinnacles. The rest of the church was rebuilt in 1840-41 by T.H. Wyatt & David Brandon in Early English style, with a nave with a South aisle and short chancel.
The six-bay arcade with cylindrical piers and stiff-leaf capitals is the main survivor of this phase. Some of the capitals are thought to incorporate 13th Century work. In 1870 Wyatt remodelled his own church with new roofs, extended the chancel and added a shorter North aisle. There is an alabaster reredos of 1887 in the church by S. Gambier Parry with mosaics supplied by Powell. The font is Perpendicular in style but completely reset by Wyatt. There is stained glass by Joseph Bell. Also windows by Hardman; A.K. Nicholson; and Lavers, Barraud & Westlake.