Anyway I still went to Shawell this morning. I had just mentioned to Steve Nichols that an early juvenile Caspian Gull would be nice and then wham I spotted one.
Juvenile gulls can be tricky, but there are some clues that can help with identification. In the very poor quality image below you can see the very plain brown upperparts with the trademark Nike 'Swoosh' across the upper edge of the greater coverts. The head is already fading to white and the tertials have broad white edges almost like finger nails. The juvenile bill does not look quite as long as some adult yet. The feathers near the bill wear with age, which makes the bill look longer. This is probably the earliest record of a juvenile Caspian Gull in Leicestershire. Post juvenile moult will start in August, but right now it is a really fresh looking juv - trust me not the crappy photo.