This bird was located just before 20:00, c20 mins before light failed completely and in already dull, cloudy, rain threatening conditions. These images are the best I could obtain. At the moment I have aged it as a 2cy on the basis of broad tertial fringes and a consistent feature in the videograbs of the raised right upperwing are the pale inner primaries.
Dick Newell kindly commented re the age as follows: "It looks like a typical 1st winter bird, but the tertials have rather broad white fringes like a second winter. I don't see any 3rd generation grey feathers in the scapulars, which I would expect for a 2nd winter. So, either a rather advanced 1st winter or a delayed 2nd winter. Would need better pictures to be sure which it is. Probably, as you say, a 2nd winter (=2CY). But Caspian Gull, yes."
Alan Dean kindly commented as follows: "Yes, looks like a Caspian. As you say, images not overly clear in failing light but what can be seen of mantle and covert pattern look quite like a 1 cy in some respects but the tertial pattern in image ‘a’ (for example) looks to have the more complex terminal pattern of a 2cy and this would also explain the rather short primary extension i.e. outermost primaries dropped during moult to 2W."