Dark slaty grey mantle and yellow-legged gull(South Korea) (1 Viewer)

Large White Headed Gull ID - South Korea

Hello everyone!
I am South Korea Birder and I like gulls.
Now, I have serious problems.

Some times ago(at 2015-10-09), I watched very strange LWHG at Incheon, South Korea. When I watched this gull, I thout that it was Mongolian gull(L. vegae mongolicus). But this gull's upperparts was too dark grey more than Mongolian gull(L. vegae mongolicus). And dark more than Heuglin's gull(L. heuglini taimyrensis). And this gull's leg colour is bright yellow similar to Yellow-legged Gull(L. michahellis). This gull's structure and bill shape is slightly different from Heuglin's gull.

Well, I have no experience like this gull.
What's your opinion about this gull?

More photoes here
http://gulls.tistory.com/51

looks like a taimyrenis to me.

Tahnk you lou.
Yes, it look like a taimyrensis.
Pale slaty grey mantle, yellow leg, red orbital ring, slightly slender bill, progression of post-breeding moult.
But It has different head pattern.
It has more sqare head line than taimyrensis.