Russ Sherriff took these great shots of this interesting looking Chiffchaff on Monday as it fed in the reeds by the Purfleet Hide on Monday.
I reckon that there is a good chance that this is one of the eastern forms aka a Siberian Chiffchaff.
The buffy brown colouration, good supercillium, slightly gingery ear coverts, olive hued wing feather edges, very white underparts and very black legs all point in this direction…