The first church at Stanmore Magna (Great Stanmore) was nearly ½ mile to the south of the present church. In 1889, when the Harrow & Stanmore Railway was being constructed, the footings of the 14th century church of St. Mary were unearthed near the Wolverton Road bridge. A tomb still remains in the back garden of a private house in Old Church Lane. There had been a Saxon wooden church on the same site, and a study of the Domesday Survey has shewn that there was possibly a Roman compitum shrine here.
St. Mary's was abandoned in 1632 and replaced by a brick church which still stands beside the present church. The brick church, dedicated to Saint John, was consecrated by Laud, Bishop of London, on 17th July 1632. By 1845 this church had become unsafe and, as it was also too small for the growing parish, it was decided to build a new one. The foundation stone for the new church was laid in the presence of the Dowager Queen Adelaide who was living at nearby Bentley Priory. On 16th July, 1850, the Bishop of Salisbury consecrated the present church. It is built of Kentish Rag and Bath Stone in the Early Decorated style of the mid-nineteenth century. The architect was Henry Clutton.
The brick church was sold to a contractor to remove, but local resentment was so strong that only the roof was removed before the arrangement had to be canceled. The ruin of the brick church is now a Grade II listed building.
The churchyard contains over 1000 graves.Amongst the distinguished resting here are William Hart, eldest son of Shakespeare's sister Joan; Sir William S. Gilbert, of Gilbert and Sullivan fame; Lord Halsbury, Lord High Chancellor of England; and Frederick Gordon, founder and Chairman of the Harrow & Stanmore Railway Company and the Gordon Hotels Company (now part of Grand Metropolitan Hotels).
Information from "A guide to the Parish Church of Saint John the Evangelist, Great Stanmore, Middlesex" (Friends of Saint John's, 1965) and original research by Peter G. Scott, 1983
Last modified 26th December 1996