The church, with its 80 foot west tower, sits in a prominent position on a hilltop overlooking the town harbour and was traditionally an important landmark along the Thames Estuary. It was rebuilt using Kentish ragstone and flint rubble in the late 15th or early 16th on the site of a previous church, possibly dating back to the 13th century. The 14th century chancel may also have survived the rebuilding, along with a pre-Reformation piscina near the altar. A brick porch was added in the Tudor period. At various times since then, the church has been altered or extended, mostly notably between 1837 and 1840 under the rector, Rev. Robert Eden. In 1872 the chancel was extended eastwards by the architect C. F. Haywood, and the south aisle was added by Ernest Geldart in 1897 as the population of Leigh-on-Sea continued to grow. The lady chapel, designed in 1913 by Sir Charles Nicholson, was added as a memorial to Rt. Rev. Edward King, a former Bishop of Lincoln and uncle of the rector at the time, Rev. Canon Robert Stuart King. King had succeeded his father as rector, and between them they served the parish for over 90 years. The church contains a number of stained glass windows, including work by Frederick Preedy, Franz Mayer & Co. and James Powell and Sons. The chancel reredos and lady chapel screen were designed by Geldart and the war memorial by Nicholson. The 15th century font was originally at St Swithin's Church in Norwich.
Leigh Rectory was commissioned by Rev. Robert Eden after he became rector in 1837. Located on Broadway, it was completed in 1838, replacing an older rectory erected under Rev. John Davey Hodge. As well as the construction of the rectory building and gardens on a 6 acre site, the work involved the creation of Rectory Grove as a public right of way, replacing a cliff-top path called Chess Lane. The building now serves as the town library but is only one-quarter of its original size, the rest having been demolished after it was acquired by Southend Corporation.
Rectors
The earliest name on the list of rectors at St Clement's Church dates from 1248 Other early rectors include Rev. John Sym, a Scottish-born Calvinist who was the author of Lifes Preservative Against Self-Killing. The following have served as Rector of Leigh-on-Sea since the Restoration:
