St. Mary's Church & Kedermister Library is open to the public on Sunday 2 August & Sunday 6 September 2009, 2.30 - 5pm. They are also open for Heritage Open Days on Saturday 12 September 2009 from 10am until 1pm.

Originally, Langley Marish was part of the parish of Wraysbury. However, it was several miles from the parish church, so they built their own church, the Church of St Mary the Virgin, in the 11th or early 12th Century. Even though, it was 1639 before they had their own vicar living there.

The church was rebuilt in the 13th and 14th centuries, but by far the biggest changes took place in the 17th Century. This was at the behest of Sir John Kedermister. The Kedermister family had lived in the area since the mid-16th Century. Edward, Sir John's father, had restored the royal park and rebuilt the manor house. King Charles I granted the Manor to Sir John in 1626.

As well as having the church enlarged and restored (which included the building of a new bell tower, a pulpit and the south aisle), Kedermister financed the building of a library (see our separate article on the Kedermister library) and the almshouses on the south side of the church. (The almshouses on the north side were built later in the century by Sir Henry Seymour.)

Sir John Kedermister also built an ornate pew for use by him and his family. Beneath this is the Kedermister family vault. The pew was later used by the Seymour and Harvey families, who owned the Langley Park estate after the Kedermister family.

The church has been named by Simon Jenkins as one of 'England's Thousand Best Churches'.