worth matravers church, dorset

the interior of the porch has large scale zigzag around it, looking late c12. could it have come from the north doorway of the nave? it is big boned for a doorway, and just might have been brought from elsewhere, but was either a doorway this shape, or a large chancel arch, given the shapes of the voussoirs. the thing is, why would anyone do such a thing before antiquarians became interested ? then again, plenty of arches are missing from corfe castle, there's nothing left of the chapel in the keep for example.