What letters preceded the name on the Royal Yacht Britannia
HMY HMS/M HMVS HMSm His Majesty's Ship H.M.Y. HMSAS Her Majesty's Ship HSwMS Her Britannic Majesty's Ship His Britannic Majesty's Ship
hmvs his majesty s ship hms m her majesty s ship her britannic majesty s ship hmy his britannic majesty s ship hmsas hmsm hswms h m y
h m y
WikipediaEntity
H.M.Y.