St John the Evangelist Church was built by Scott and Moffatt in 1846 when Wembley became a separate parish, largely at the instigation of the Copland sisters, who were influential local benefactors. Anne and Frances Copland, who in 1843 inherited Sudbury Lodge and its estate, offered land nearby for a church to serve the southern part of Harrow parish. In spite of opposition from local farmers, who preferred a site on Lord Northwick’s property on Wembley Hill, the sisters’ offer was accepted since they would bear all the cost of building. St John the Evangelist’s was built of flint with stone dressings with nave, chancel, north-east chapel and wooden bell turret.

In 1859-60, Scott added a new north aisle to the church, with a gallery for the organ and children. Further extensions were carried out in 1900 and 1935.