I was up above the Dyfi this morning at Glandyfi at high tide. It would have been about 8 o'clock-ish and a flock of 65 Barnacle Geese flew in to the saltings on the other side of the river, quite some distance away, unfortunately.
Accompanying them was a noticeably smaller, dark brown, goose with a pale tail. I can only think of one species that it might be. I know its very unlikely but it might be worth checking the flock out for a Lesser White-front.
Or it could be some strange feral bird, of course.