Technically almost all unmarked mute swans on open water in Britain belong to the monarch. There’s a terrific blog post here that goes into the fascinating legal history of this prerogative.
However there is an exception; ownership of unmarked swans on the reaches of the Medway around Maidstone was granted to the borough by Elizabeth l (or maybe James I). So the swan I photographed on Wednesday is the responsibility of the Mayor of Maidstone.
Read more about Medway swans here.