The original building was a small aisle-less church built around 1135. it was entirely rebuilt and enlarged in the second half of the 13th century. The upper part of the tower seems to have been reconstructed in the late 16th century, when the south brick stair-turret was added.
The North aisle is old. The arcades are low and have quatrefoil piers with later arches.
Since 1850 some rebuilding of the South aisle took place when the wooden porch outside was added, and also the spire. The vestry was added a the north-east around this time. The timber ceiling also dates from this period, as do the pews, the wooden eagle lectern, and the pulpit. The pulpit contains wooden panels removed from ‘New Place’, the demolished Tudor manor house of Gilston, which stood near where Gilston Park is now.
The lancet windows in the chancel are of the 13th century. The East window is 19th Century, but also has fragments of ancient glass. The North aisle had a two-light 13th century window and two others copied from it, or restored, in the North wall.
The East window in the aisle is modern. The West window had old double-chambered jambs but a modern head. There is one piece of 15th century glass in it depicting the arms of Sir William Estfield, who was Sheriff of London in 1429 and went on to become May of London in 1437.Round the edge are the words Ora Pro Anima Willi Estfield Militis (Pray for the soul of William Estfield, Knight) in black letters.
This is a survival of first-rate importance: evidently late 13th century, and well enough preserved to have made reconstruction possible. There is a tall dado, with thin shafts only 2 feet long, with trefoiled pointed arches and stylised flowers in the spandrels. The top goes straight across the chancel.
This is hexagonal, and 12th century, the only survivor from the earlier church. It is made of Purbeck marble with shallow blank arches on a 14th century base. The lid is Victorian.
There are two good mid 17th century epitaphs: on the South wall of the
sanctuary Bridget Gore + 1659, a white standing figure in shrouds in
front of an oval black niche, drapes flanking left and right. This type
had been made popular by John Donne’s tomb in St Paul’s Cathedral.
Opposite, on the north wall, Sir John Gore + 1659, black and white flanked by black columns; and a curly broken pediment with a small figure on it, signed by Joshua Marshall. There are also a good collection of 17th century marble ledger stones to the Gore family in the sanctuary and chancel, showing the sad extent of child mortality at the time..
The organ was built by Bedwell & Sons in the early years of this century. It was never intended to be a church organ, as it was built originally for the drawing-room at Gilston Park, and was given by the squire. It was rebuilt in 1939 by Arnold of Thaxted, but at the present time it is unusable.
The West doorway is late 13th century. The blocked doorway in the North aisle belonged to the former church.
The combined piscine and credence are late 13th century, and low down because the chancel floor was raised in the 19th century. The windows in the chancel are of the 13th century.
There are two bells in use, going back to the 17th century.
There is an almost unbroken line of incumbents since the first recorded Rector of Gilston in 1336.