Located in the pretty village of Walkern just over two miles from Stevenage, this small oblong Saxon building has an apse at the altar and dates from the middle of the 10th century. The building stone is 'clench' and imported limestone. The church of St. Mary has experienced a number of additions with the exterior of the building taking its present form in the late 19th century. The interior of the building has a number of different influences including the south wall which is Saxo-Norman with two un-moulded arches and the Elizabethan octagonal oak pulpit. There is an opinion that St Mary's is the oldest church in Hertfordshire.