Twenty-five years after the opening of this thread, the pre-1940 history of this song remains obscure.

All we know for sure is that the success of the pop song led composer Fred Godfrey to report in 1941, with some circumstantial detail, that he'd written it, or something much like it, in "1916" (actually 1917) while serving with the Royal Naval Air Service in northern France.

That's about it. Disappointing, isn't it?