The Parish Church of St Andrew in Boxford, Berkshire, England, stands on the south bank of the River Lambourn and preserves fabric from many centuries of English church-building. The visitor enters the church through a medieval door hung in a 13th-century doorway. Much of the structure is 15th-century, while significant portions descend from the 11th-century Anglo-Saxon church whose surviving window — Britain's oldest working example — predates the Norman Conquest. In 2011, restoration of the chancel's north wall revealed another long-hidden Anglo-Saxon window concealed for some 150 years. The nave and chancel are built of cement render with Bath-stone dressings and tiled roofs, while the tower and north aisle are formed of banded flint and brick with Bath-stone dressings, giving the church its distinctive West Berkshire character. - AsNotedIn

[The window] is a wooden frame made from oak, with an oak shutter on a string side hinge which probably would have been made from hemp. It has been described rather inelegantly as an ancient cat flap. Although it hold a working shutter, the window cannot open fully nowadays due to an enormous monument on the inside of the building.