Observed looking down from cliffs at Tenby. Regular dives - looks like small penguin on first impression
No interactions present.
Thanks for your id Syrphus I have added another picture (still rather unclear as it was taken at distance) - this time in profile of the bird moving in the other direction. I agree that the bill does appear chunky although whilst viewing the birds it did not seem to be as prominent.
I think syrphus' point is that the bill is not long and pointed as Guillemot's is.
Paul Seligman. Flickr: http://www.flickr.com/photos/paul_seligman_cardiff/collections/721576087...
Lat/Lng: 51.64, -4.7
OS grid ref: SS132969