early C15, restored in 1790 by Thomas Telford when north aisle was demolished and again by George H. Birch in 1885-6
slate roofs with coped verges on carved stone kneelers.
Tower: Early C13 to bottom four stages with chamfered plinth and string courses
Top stage with embattled parapet added c.1400.
Conical plain tile cap with C18 brass weathercock on contemporary finial.
Late C14 west window has heavily restored panel tracery in 4 lights
Rebuilt in present form c.1300 but roof heightened in C18, refaced and present windows inserted in late C19.
Infilled pointed arch immediately to right of westernmost window in south wall, which cuts apparently C12 infilled round-headed window.
Main feature is heavily renewed late C12 six-bay south nave arcade: circular piers (one with plain moulded base visible) and square abaci with single-stepped round-headed arches.
Eaves line of C12 nave visible on south with two single-splayed chamfered lancets alternating with two chamfered roundels to former clerestory.
Early C13 double-chamfered tower arch with corbelled responds and imposts.
This has pointed arched recess in east wall and pointed arched recess with inner trefoil-headed recess (probably formerly housing piscina) to east in south wall, both probably early C14.
Three tomb recesses in south wall also early C14, 2 to east with 3 orders of roll and fillet moulding (easternmost with ballflower enrichment and inner trefoil-headed recess) and that to west double-chamfered.
Infilled moulded half-arch in south wall of chancel looks C13.
Fittings and furnishings including pews, choir stalls, pulpit, lectern and low stone wall with marble coping separating chancel from nave and aisle mainly late C19 or later.
Oak chest in recess with ball- flower decoration has painted lettering "John Lloyd and Tho.s Oswell Church Wardens 1775." Stained glass in east window by Kempe , in south wall of chancel 1912 and in east window of nave 1920.
Monuments.
This has wall memorial to Thomas Corbet at east end: Corinthian capitals enclosing inscription panel with heraldic device above.
North wall of nave has C19 wall tablets and memorials and a memorial to William Basnett , a justice of the peace for Middlesex: rococo style with an urn in front of an obelisk, which has an heraldic device attached.
Four C18 hatchments in south aisle and three in nave, which also has royal coat-of-arms of George III fixed to north wall.
The church was collegiate in the Anglo-Saxon period.