 Much of the viaduct's stone quality and some workmanship at the west end were only just adequate for the purpose ... but the flat-stone, lime-mortar-bedded, pier hearting carried up to 1.5 m above arch springing was an effective feature which had probably saved the piers from collapse.In cross-section, the spandrels presented an unusual application of the classic gravity retaining wall.In the later decades of the twentieth century the viaduct had fallen into an ever-worsening condition, with much serious erosion and loss of facings; the western arch had sagged and the second arch had hogged; cracks up to 60 mm had opened up in the extrados of the arch rings.