Stupid boring history lesson coming up: It was somewhere around 1650 that Charles II regained the throne in England. Cromwell screwed up badly enough that the english people literally begged for a return of the monarchy. British navy ships during his period didn't carry the HMS title when he was king. They used HBMS, meaning, His Britannic Majesty's Ship. So, ships from this period, like HMS Britannia, were called HBMS Britannia in their day. You there in the back row, WAKE UP. Straight to the Principal with you, young man.