A geological survey of about 120 medieval churches in south Cambridgeshire reveals a dominant theme of local fieldstone rubble walls with dressings of local Cretaceous Clunch and imported Jurassic Barnack limestone; the richer the church the greater the volume of costly Barnack. The Cretaceous Ely Sandstone forms rubble walls only near the city. Victorian renovations to the medieval fabric of south Cambs churches used a much wider range of stone from the Lincolnshire Limestone Formation and further afield, made possible by new canal, then rail, networks. St Laurence at Foxton, for example, has fieldstone rubble walls, partly rendered, with medieval dressings of Barnack and Clunch, much repaired with Bath stone in the nineteenth century.