Why is Ken Russell’s ‘The Devils’ rated X?

Based in part on Aldous Huxley's 'The Devils of Loudun,' Russell's film uses 17th-century France as a vehicle for a ferocious indictment of church-and-state corruption.

A nun in a white habit kneels beneath a crucifix inside a stark tiled chapel surrounded by rows of other nuns.

Observer movie reviews: Ken Russell’s ‘The Devils’

Why is Ken Russell’s ‘The Devils’ rated X?