The parish began in a Regency house, once home to Baron Sir William Congreve, the father of modern rocket technology.
St John's is a local landmark and focal point in a prominent position: it stands on an island surrounded by roads and housing.
It is built of Kentish ragstone, a local material, and has a roof of Welsh slate. The architectural style is largely Perpendicular, which which was out of fashion by the 1850s, but there are also some Decorated elements. The architect Arthur Ashpitel, who worked extensively in Kent, was associated with Anglican evangelicalism; this may have led him to use the Perpendicular style, which was popular with that movement.
Inside, the fittings date mostly from the late 19th century and include a rood screen and reredos by HS Rogers. The firm of Heaton, Butler and Bayne designed many of the stained glass windows. Some windows in the north aisle were destroyed during World War II and were subsequently replaced.