In a letter of 1919 to Bernard van Dieren, a composer whom he greatly admired, Philip Heseltine explained how he had submitted a group of songs to the publisher Winthrop Rogers under the pseudonym of Peter Warlock, having failed to find a publisher under his own name. The ruse was soon revealed, but not before distinguished singers of the time had started to take an interest in them.

Born in London in 1894, Heseltine had been encouraged in his musical enthusiasms during his time at school, latterly at Eton. There followed an introduction to Delius, who continued to show an interest in his work, and after study in Germany and a year at Oxford reading Classics, he turned his attention to the study of earlier English music, although himself without formal musical training. As a pacifist, in any case medically unfit for military service, he spent the war years in Cornwall and then in Ireland, before returning to London, the centre of his later activities, broken by a period with his mother in Wales and a time in Kent. A certain instability of character, evident, perhaps, in the dual Heseltine/Warlock identities, has been attributed in part to the early death of his father in 1896. Peter Warlock died in December 1930 of gas poisoning, whether by accident or suicide.

Warlock is remembered in particular for his Capriol Suite, an attractive reworking for string orchestra of French dance music of the sixteenth century, also arranged for piano duet and fuller orchestra. A number of his carols have a firm place in Christmas choral repertoire, while his many songs form a remarkable body of work, influenced by Delius, Van Dieren, and the Elizabethan and Jacobean composers that had formed the core of his musicological studies as Philip Heseltine.