I found this unusual gull this morning at Hayle Estuary from the Old Quay Inn car park at high tide in misty conditions. The jizz and pale colouring gives the appearance of a Glaucous Gull but the dark primaries sounded alarm bells. Glaucous-winged Gull had been considered but primary pattern, bill colour and general jizz is wrong for that species. Independent discussion with local gull enthusiasts have all confirmed this bird as a hybrid.
Thanks to John Chapple, Martin Elliot and Mashuq Ahmad for discussing the features.