Parish church, with ragstone walls containing Roman, and later, brick. The lower part of the tower appears to be C11 (Late Saxon rather than Early Norman, and potentially dating to the establishment of the Benedictine Priory in 1046). One S. and one N. window, and the tower arch, are probably also of this date. The tower has no buttresses but Roman brick quoins. The upper part of the tower (with bell-openings and battlements) is probably C14. Much of the chancel and nave was rebuilt in the C14. The north porch was added in the C15. Some rebuilding took place in the C16 (the upper part of the chancel was rebuilt in brick) and in the C18, when the s. vestry was added. Nave heightened in brick in 1833, when the s. arcade was rebuilt.<3>

Features and fittings include: C11, C14, C15, and C16 windows and window details; a doorway with C16 head and earlier jambs; C14 north doorway; early C16 chancel roof; north porch has two stone corbels for former roof truss with carved half-figures of angels; probably C16 chest in tower; C13 coffin lid in chancel; C14 or earlier painted consecration crosses on chancel east wall; early C13 Purbeck type octagonal font.<1><3><5>

Fragment of Saxon carving built into the s. aisle wall by s. door: C10-C11 grave cover?<2><3>

The hall, to the south of the church, was added in 1971 and extended in 1992.

According to Rodwell & Rodwell, apart from the tower, the church is of little interest architecturally but it may conceal a lot of archaeological information. Nave foundations, they suggest, are probably at least as old as the tower. There is an interesting change of direction in the wall of the south aisle (not distinguished on RCHM plan), in sympathy with the misalignment of the tower to the general axis of the building. It is possible that the east end of the aisle incorporates a south transept, or a porticus (since it overlaps the chancel substantially). Graded Aib by Rodwell.<4>

In 1989 two holes were dug against the north wall by the parish to check the depth of foundations prior to lowering of ground level. The depth of the foundations seemed to be 1.4m below ground level. A change in the foundation construction in the hole to the west of the porch indicates that at some time part of the nave wall was rebuilt. In the hole to the east of the porch, substantial stone foundations were observed. In neither hole was the natural subsoil evident.<7>

Test pit dug to 1.2m by south wall of present church hall (1990). Natural not seen. Below the 150mm of topsoil was loose silty clay to depth of pit. Finds from this include 1 piece medieval peg tile (not kept) and 2 plain red tesserae (see ESMR 2214). The recorder suggests that this test pit was dug through the construction trench for the church hall and therefore the finds are redeposited.<8>

In 1991 two trial holes (A and B) were excavated in preparation for the proposed West Mersea Church extension (a third trial hole C was dug but abandoned after modern pipes were uncovered).
Hole A (1.5 x 1m) was sited on the line of the proposed foundations for the eastern extension. Below the topsoil to a depth of 1.12m was a homogeneous sandy loam. Finds were found in both layers. These were all disturbed and appeared to have no context. Human bone was found but it was similarly disturbed; the bone was residual and did not represent an ‘in situ’ inhumation. Two coffin fittings (handles and a nail) also seem to be associated with residual deposition of graves. Other finds included peg and flue tile, and two sherds of pot, one sherd possibly being Roman.
Hole B (1 x 1m) was sited on the line of the proposed foundations for the western extension. Below the topsoil was a sandy loam to an arbitrary depth of 76cm. No features were found but residual finds were made suggesting that the material had been redeposited. Finds of human bone, slate, tile (of varying ages) and sherds. The sherds ranged from Samian ware to medieval and post medieval. <9> <10>

Site Assessment = The west tower is a good example of early masonry.<1> Church is in small original village area of what is now a seaside resort.<3> Church and priory (west of church) are underlain by one of the most substantial Roman villa complexes in Essex. "There is no need to elaborate upon the archaeological significance of the area - it is one of the most crucial in the diocese and any opportunity, however small, to investigate any part of the archaeology of the church, above or below ground, should not be missed. A substantial opportunity presented itself in 1972 when a vestry was built on to the S side of the aisle and the ground was lowered.

Six digital photographs, in the Colchester HER, were taken in July 2016.<11>