St Denys is a beautiful and spacious Grade 1 church dating back to about 1430. The chancel is built of cobblestones, with coursed freestone rubble elsewhere, all with ashlar dressinqs and embattled parapets. The impressive rood loft staircase has three doorways and a squint. The chancel has a finely worked large alabaster figured monument, 1641, to Sir William Dyer and his family. There is also a purbeck slab with inscribed copper plate, 1389 to Alianora Braybrook in the chancel south wall. Fraqments of C15 glass, including a whole angel, are found in the north chancel window. Other qlass is by Heaton, Butler and Bayne, London and dates from 1893. The nave retains its C15 foliate bosses, carved braces and figures, and angels in centre of each bay holding shields and emblems of the Passion. The large spire is 156 feet high.
The project helped to publish a guidebook to the church by local historian Thelma Marks.
Little is known about the bats at Colmworth. The church community lives in harmony with the bats and no surveys have been undertaken.
Bedfordshire Bat Group led a bat walk in 2021 around the church.