It is a quirk of our monarchy that the reigining sovereign 'owns' all the swans in England, apart from some in the hands of the ancient Vintners and Dyers Companies. Not sure if she's really that fussed about where they all are, however, although she only claims ownership of those found on certain stretches of the Thames and surrounding rivers. I spotted this one a short walk away from my house, going along the Basingstoke Canal. Best I could muster I'm afraid, as I haven't been 100% today.
Thanks, Jean, for researching the swan info for me!