That seems to be it then. Chrysler Airflow it will be - with my thanks for all attempts to ID.
Much success at Farmwood Reservoir yesterday as we ticked White-winged Black Tern, Black Tern and the mega American Black Tern. They are hanging out together and at various times could all be seen grouped in the telescope field-of-view as they rested on floating pontoons of some sort. That is a sight which we are unlikely to see again. Hopefully they will eventually separate the species as ABT and BT. Ring-necked Duck later at Westport - another American job.
'Find your enemy and shoot him down - everything else is unimportant.'