Sacrificium was commissioned by the St Albans International Organ Festival for what has become one of the most influential organ competitions in the world. It is a demanding 8 minute work that will challenge performers with an abundance of contrasting material whilst still leaving space for individual interpretation. Casken refers to the story of Alban who sacrificed his life to save another Christian thereby becoming the first British Martyr in his programme note and more specifically the act of exchanging cloaks and deception which led to Alban's execution. This idea of taking on a new appearance is apparent in the music as recurring themes undergo transformations, gradually becoming absorbed into new musical textures.