This Is what I signed as an Officer Cadet (Midshipman) in 1972.
“I swear by almighty God that I will be faithful and bear true allegiance to Her Majesty Queen Elizabeth II, her heirs and successors and that I will as in duty bound honestly and faithfully defend her Majesty, her heirs and successors in person, crown and dignity against all enemies and will observe and obey all orders of her Majesty, her heirs and successors and of the generals and officers set over me.”
I cannot however make any comment regarding your reasons, re;
Firstly because the monarchy etc;