The strange case of the juvenile LBBGs, Pennington Flash

From the sublime to the ridiculous, hot on the heels of the identification challenges of the superb 2nd summer Cape gull comes this, an arguably even more difficult bird to identify.....and even more interestingly, where is it from and how did it get here? 

It's obviously a juvenile gull and one of four currently off the car park at the flash, two very young birds and two slightly older, but did they really make it here under their own steam? And if so where from? A possibility is that they were brought here by humans, perhaps when a nest was disturbed, but it still seems that they must be locally bred. I mean you don't go to Llandudno, find four juvenile gulls and bring them back to Pennington Flash..... do you? Surely you'd release them at the nearest park lake you can find.  And what species are they? Black-headed gulls breed at the flash, but they're clearly not that species. They're a large gull and either lesser black-back or herring gull. My best guess is lesser black-back but I'm not sure that I can be certain.

I'm not sure we can call these flight feathers! I suppose they do the job for very short flights but it's hard to see it getting very far with these. If this bird had flown over my garden on its way to the flash, as many birds do, it sure would have given me palpitations.

I'm not sure that we can even call this a juvenile. It's more like a fledgling. Look at the down around its head. It could have been in the nest yesterday!

Apparently lesser black-backs breed as close as a couple of miles from the flash so I guess that might be the source of origin. Perhaps these birds moved from whichever roof they were on due to the current extreme heat, in search of somewhere cooler and water. 

The two very young birds were also with a couple of slightly older juveniles, presumably from the same brood. These birds probably can fly quite well and make me doubt that the group was brought here by humans because I doubt that these could be easily captured. That said, there are no adults with them. I called in twice today to see them and there were no adults anywhere near. It's hard to believe that four such young juveniles could make it here together on their own. 

Four little egrets, possibly two adults and two juveniles, were in Ramsdales and a single common tern was fishing over the flash. Up to 40 swift were over the flash and ruck.