Of course I should have added that "no trace of Godfrey's song, or any presumed predecessor, is known to survive."

Wikipedia assumes nevertheless that "it is likely that the song existed earlier [than 1917] in various forms in all divisions of the British military."

Nonsense.

The fullest and best source of information is at

http://www.fredgodfreysongs.ca/Songs/Bless_em_all.htm