After Andy sighted what appeared to be a Glaucous Gull at Epney early this afternoon, It rather frustratingly flew off before I could get to out, despite me being only a short distance away checking the river at Longney. My frustration soon turned to joy though as I eventually managed to track it down at 2.00pm down-river at Priding (photo above). I got good views of it, especially when it moved closer, before it and most of the other gulls took off and headed towards the estuary at 2.40pm. The bird is now believed to be an albinistic Lesser Black-backed Gull.
Some more photos are below, I was puzzled by its size at the time, and its very white plumage, and the bottom photo gives a chance to compare its size next to another Lesser Black-backed Gull, in front, and the much larger Great Black-backed Gull, behind.