This bird took me completely by surprise. It flew in over the north end of the lagoon and then south over lagoon when I lost it being mobbed. 5 minutes later I picked it up again whilst scanning through the duck, it was sat on the nest box on the other side of the lagoon. Over the next 50 minutes the bird flew around the lagoon to various perches and was last seen heading north-west. This appears to not be the Canvey bird based on the size and strength of the breast patch. You can also just see the metal ring on the left leg.
The images are not sharpest and a little grainy due to the poor light and they're digiscoped.