British Common Law contains the notion of Royal Prerogative which includes such important powers as the dissolution of Parliament, calling an election, declaration of war, the awarding of honours and many others.

Under Royal Prerogative, only the Monarch has the power to do these things, although as a constitutional monarch they are almost always done under the advice of the Prime Minister.

There are some historical quirks of this, one of which is that the Monarch owns all wild swans living in open water - of the species called 'mute' swans. Other species of swans, and those owned by individuals are not owned by Her Majesty.

Contrary to common belief among some people (including some British people) it is not treason to kill a wild swan and it does not carry the death penalty.

Incidentally, the Title "Queen of England" has not existed for over 300 years - she is Queen of the United Kingdom of Great Britain and Northern Ireland.