Derby Telegraph | June 24, 2026 AERNARFON Castle has witnessed many historic events but nothing like the mustering of an army of twitchers in the shadow of its formidable ramparts. Sieges, sackings or royal investitures were far from the thoughts of the binocular-wielding cohorts advancing on the medieval bastion with a single objective - seeing the first western reef heron to arrive in the British Isles.