It is considered an offence to kill a wild mute swan as it is believed they are the property of the Crown, though centuries ago, their meat was considered a delicacy.
The birds are now protected under under the Wildlife and Countryside Act 1981 and killing or injuring a swan used to be classed as treason under a law dating back to the 12th century.
Why does this remind me of The Pirates! Band of Misfits movie from last year?
*Not that I condone the random eating of swans or anything.