Liturgy is a formal act of worship or church service, as opposed to private devotion, involving a prescribed form of words and ceremonies spoken and performed by the priest and sometimes by the congregation. In Christian churches, the Christian year forms the basis of the liturgy, and in some medieval churches, Latin liturgical drama based on stories from the life of Christ was enacted. Vernacular mystery plays may have developed from these. The term was sometimes used as shorthand for the Book of Common Prayer. Under Archbishop Laud and again with the High Church revival in the 19th century, the liturgy was particularly valued. It was deeply disliked by the Puritans and their successors. Seventeenth-century poems on the passion of Christ, for example by Richard Crashaw, or George Herbert’s ‘The Sacrifice’, owe a good deal to liturgical tradition, as does John Keble’s phenomenally successful Christian Year (1827).