The bird showed well until at least 5pm when the last 4 of us left it (14 people saw it today?) - at that point it had sat in the same place for perhaps 30 minutes and, after a look around Porth Clais, I had one final look for it at 5.30pm it wasn't there. My guess is that it had gone to roost as the insect activity had stopped by then. It favours the hedge that runs at right angles to the road, by the 5 bar orange gate, at the top of the hill out of Porth Clais towards Rhos y Cribed SM 737243. Some further information about the status & taxonomy of IS here:
In my opinion, this is a first-winter, e.g. the distinct pale tips to the greater coverts (but I am happy to be corrected), and most likely of the form isabellinus (Daurian Shrike) due to the lack of contrast between the under and upperparts (which are buff-washed), distinctly pallid appearance, and subdued supercilium.