England is only one of 4 countries which make up the United Kingdom - the others being Scotland, Wales and Northern Ireland. The Queen is the head of state for all these countries, and in general...
Formally that would be the battleship HMS Vanguard the final battleship of the Royal Navy. However there are two aircraft carriers under construction which will be the largest uet at 65000 tonnes.
The royal navy help the ministry of defence by help fighting with the conflict of war throughout the world, they protect Britain's seaways and the seaways of her colonies from attacks