You are quite right.
Indeed I just tried another file and it worked fine.
Thank you so much for your speedy and attentive help.
Really excellent.
Robert
Thank you for the explanation. I see what you mean.
In my haste to ask the question I missed an inportant point. I am in fact "round tripping" (or trying to) from another application (Capture One Pro). Capture One gives me the option to edit in Affinity Photo and will export a JPG or TIF (8 or 16 bit) which then opens in Affinity Photo.
When I have finished editing in Affinity Photo I want to go back to Caoture One Pro and continue editing or output from there.
Affinity Photo does not even take me to the same directory, is there any way to return to the source directory rather than "Pictures".