I would welcome any advice on the identification of this warbler, seen when the fog cleared at Al Rafa'a (just along the coast from Dreamland in Umm Al Quwain) on Saturday morning. Visually it was a small, distinctly grey bird with whitish underparts, long-tailed, short-winged and quite flighty; settling only for seconds and then off to the next bush. I didn't see any obvious pattern of tail movements and it was silent as it moved around. I had heard 'tchk' calls close-by earlier but assumed this was a Lesser Whitethroat seen earlier, and couldn't certainly attribute tha call to this bird.

Yes, it doesn't look quite right for either.
Sykes' was one of the first things I considered (and the only other possibility I can think of), but is there anything to suggest that it's not just a worn, greyish Chiffy? Legs are dark, there's a greenish cast to the mantle and rather more enhanced super on the flight shot.
I'm not convinced 100% either way, to be honest.
Sykes's possible, Mark? Or just a very worn Chiffchaff?
My first thought is Chiffy, Steve, but I'm totally thrown by what appears to be white outer tail feathers! Any other pics?