Spem in alium must be not just the greatest of all Tallis's musical achievements, but one of the great musical compositions of all time. The text is a respond from Sunday Matins during the reading of the history of Judith and quite why it was chosen is not apparent. Clearly, Spem in alium is an occasional piece, presumably written for a great state occasion, and perhaps the most likely was the fortieth birthday of Queen Elizabeth in 1573. Tallis was well practised in the Elizabethan art of diplomacy, and to a cultured and music-loving queen the greatest piece of music ever written would have been a most acceptable birthday gift!