Slimbridge swan project celebrates 50th year
11 February 2014 Last updated at 10:47 GMT
Fifty years ago the conservationist Sir Peter Scott made an historic discovery.
While indulging in his passion for painting and sketching Bewick swans, he noticed that each one had a different face.
His artistic endeavour has become one of the world's longest-running research projects.
John Maguire reports.