I had joined Andy Latham and John Reeves at about 2.15. They hadn't seen it but it was pretty convincing on song, lurking somewhere in the bushes beyond the small pool. It certainly looked like mission impossible to get a glimpse other than the brief flight views we managed until this happened...
Totally against the run of play and then a short while later, it paused to preen on the opposite side of the pool! That long supercilium and other features reminiscent of the 2016 bird....
And here's the bird in 'song' when it wasn't doing a perfect impression of Common Chiffchaff.
It was impossible not to have doubts but presumably this is an Iberian Chiff mimicking a Common. It was 'Iberian' when not in view but then frequently singing its heart out above our head as a 'Common' when feeding. And NO, before you query it, there weren't two birds involved...