Cultural shock is a perishable commodity, so it is an intriguing test of the longevity of contention that one of the most controversial comedies of the 1970s and one of the most disreputable novels of the 1990s are among the productions bridging the 2013 and 2014 theatre seasons.The 1977 premiere production of Once a Catholic, a comedy by Mary O’Malley, was one of a series of works in that period – including The Life of Brian and Dave Allen’s TV shows – that satirised Christianity or Catholicism. O’Malley’s play is set at a London convent school in the 1950s – specifically Kilburn in Kathy Burke’s Kilburn Tricycle revival – where most of the nuns and pupils are of Irish Catholic stock. An opening ­register-taking gag has virtually