This was when the alternative instrumentation was most likely prepared.
Principals: Louis, a farmer bar, Alison, his wife sop, Father Philippe bass, Pierre, a wandering scholar ten
Orchestra: fl (=picc), ob (=ca), cl in B flat, bn - hn - perc (sd, td, bd, cymb, susp cymb, tamb) - harp - str qnt (2 vn, va, vc, db)
The published score states that Britten arranged the orchestration of Holst's opera for the 1951 Cheltenham Festival. However, his earliest work on the arrangement almost certainly dates from November-December 1948, undertaken in preparation for a broadcast in January 1949. Britten adapted Holst's own suggestions for single wind instruments, and wrote new parts for harp and percussion.