After a while I got good views of the upperwing and the inner primaries were undoubtedly those of a Herring Gull. Note the rather diffuse pattern on the greater covert's, not quite the ecpected piano key nothces usual on Herring Gull. Another anomoly here is the absence of pale tips to the primary feathers.
Note again the remarkable blackish brown tertials. Bill can be seen well here, slightly paler at the base of lower mandible.
Best shot of the tail pattern. Well within the pattern of argentatus Herring Gull.
Here in flight and looking rather like a classic Herring Gull in flight, one would not even give it a second glance on a flight view..