RAF officers and airmen do swear an oath of allegience.
For even more trivia, the
Air Force (Constitution) Act 1917 gave the Sovereign the legal basis for forming the Royal Air Force.
Part I
Establishment of Air Force
1
Raising and number of Air Force.
It shall be lawful for His Majesty to raise and maintain a force, to be called the Air Force, consisting of such number of officers, warrant officers, non-commissioned officers, and men as may from time to time be provided by Parliament.