During the morning small numbers came to the lagoons and amongst them was a 'white-winged' gull, but not an Iceland or Glaucous Gull. It was too elegant for a Glaucous and not quite right for an Iceland. The primaries had greyish markings not unlike a Kumlien's Gull, but again I didn't feel it was quite right for one of those either.
Its wings were really long, which might suit Iceland, but too me it was a bit too Herring Gull like. At the time I thought it was most likely to be an aberrant Herring Gull.
The video below gives the best impression of what I saw. Note how its tertials seem to stand up and how thin its wing tip looks.
As always I welcome any opinions.