It is unfortunate that this debate has to have such verocity over thirty years after Bishop's death. Bishop's son Arthur freely admits that his dad rarely talked about his WWI experience. If only the information was still available, and credible.
Al notes Stewart Taylor and Syd Wise. Both are Canadian historians(Dr. Wise taught at Ottawa's Carleton University). Many with an interest in this topic have researched it to some depth, myself included. Each piece seems to link to several more.
Will there ever be an answer? Unlikely, unless we can perfect the time machine. Even then, each person's perception is just that. No one can absolutely state yes or no it happened. The jury's decision will rest on a preponderance of what they believe to be tangible evidence. What that result is, is each person's guess.
Steven E. Dieter BA BA(Hons)
Former Historian
Billy Bishop Heritage and Museum