AbstractA regional strain study of Snowdonia, North Wales, has used clast orientation data from Caradoc volcanic rocks. The data, analysed using theRf/Φ technique, have revealed that while the local strain pattern is very heterogeneous in intensity and style, it can be processed to define a regional ‘average’ strain.This regional strain closely approximates to plane‐strain in both rigid and ductile markers. This, when considered with the style of folds, leads to the tentative suggestion that the deformation mechanism in Snowdonia is one of gently inclined and ductile simple shear from the nor