Britten‘s music is usually thought of as tonal, even if the term is sometimes qualified.’ Much of the drama of his operas (at least, up to and including A Midsummer Night's Dream, op. 64 (1960)) has been discussed in terms of ‘tonal action’, as have the structures of individual songs, song cycles and purely instrumental works. Yet his earliest published works are not tonal in the same way as later, more widely known ones. Not until the works of his American years (1939–42) do we begin to see the kind of tonal structure that enabled Peter Grimes, op. 33 (1945), to be conceived – structures like the highly focused tritonal opposition of Les illuminations, op. 18 (1939), or the E/C ambiguity (eventually resolved in favour of E) of the Hymn to St Cecilia, op. 27 (1942). Nevertheless Britten's first three works with opus numbers, written while he was a student at the Royal College of Music from 1930 to 1933 (the Sinfonietta, op. 1, completed in July 1932; the Phantasy Quartet, op. 2, completed in October 1932; and A Boy was Born, op. 3, completed in May 1933), are quite clearly diatonic in basis. This essay explores the ways in which this diatonicism is structured, and sketches the subsequent history of the main procedure involved.