Ben Oakley was Bandmaster, the Band of the Pioneer Corps for quite a while during the 2nd World War.  He was never their Director of Music because he hadn't attended the appropriate course at the Royal School of Music, Kneller Hall but was 'commissioned in the field', I understand, to replace whoever was Bandmaster/Director incumbent of the job beforehand.  The history behind how he even came into the Pioneers Corps (since he left the Duke of York's Royal Military School to become a Band Boy in the Royal Artillery at the beginning of the Great War) is totally obscure at present.