Composed in 2021 to commission for the Choir of Westminster Abbey and dedicated to Westminster Abbey Choir School. This is MacMillan's fourth mass setting for exclusively choral forces, following the early Missa Brevis (1977), the Mass for Westminster Cathedral (2000) and Missa Dunelmi, for Durham Cathedral (2011). St Edward the Confessor, one of the last Anglo-Saxon kings of England, re-founded Westminster Abbey in 1065 when he rebuilt a Saxon church at Westminster and dedicated it to St Peter, making St Peter's Day one of the most important festivals in the Abbey calendar. Mass of St Edward the Confessor was first performed on St Peter's Day 2022, thus honouring both the patron and the founder of Westminster Abbey. Lasting 15 minutes, the work explores a wide range of moods and choral textures in response to the text and is suited to liturgical and concert performance alike.