While Fred Godfrey was conscripted into the RNAS in 1917, in 1918 the RNAS and the RFC amalgamated to become the RAF and it was from this service that Fred Godfrey was demobbed in 1918. That may explain the non-naval ranks mentioned in the song. As his Grandson and biographer Barry Norris explained once adopted by the RAF the song "percolated" and evolved over the years, that may also explain the other anomalies detailed by Lighter in his posts.