The answer is for centuries, even possibly the beginning of time. Most cultures have a reference to a swan as being part of the beginning of man, the earth or part of their mythology: Hopi & Mohawk tribes, Children of Lir (Ireland), Aborigines (Australia), Greek Mythology (Leda & the swan), Lohengrin (Germany), etc.

The swans throughout Europe use the U.K. as part of their migratory path. It is said that Queen Beatrice of Cypress donated a mating pair of swans to King Richard (The Lion Heart) during the Crusades. Even though this may be part of the lineage of the U.K. swans, in all probability, the swans were most likely already settled in parts of the U.K. due to their migratory flights. The Regal Swan