I gave no consideration to whom I swore allegiance when I joined the RAF. I guess I would have sworn it to anyone if it meant I got in and trained as a pilot - obviously there are some who would not be included in that list. You must remember that when I joined the National Anthem was played at the end of the night in a cinema and most would stand still for that so it was natural to swear allegiance to the Queen on joining the services.
Having said all that as an older chap I am happy that it was to HM. Really your allegiance then, as now was to your colleagues, and probably senior officers if the truth be told.
ACW.