As you can see from the photo above, the threaded section isn't all that long, and it's also awkward getting a micrometer in there due to the nut flange. However, I gave it a going-over with a marker pen and rolled it on to an eraser - nice pattern...
6 thread peaks produced, measuring - as accurately as I could with a micrometer - ~5.16mm between the outer ones, which means fractionally over 1mm thread pitch, but quite possibly exactly 1mm allowing for line thickness and other accuracy factors.
OD of thread is 9.48mm, so I'm guessing that's M10 allowing for clearance?
Pretty sure it is M10 x 1, then, unless there's an alternative thread sizing that conforms to the above? I can't find one, tho'. It certainly isn't 1.25mm pitch.
Just need to confirm whether a Tohatsu fitting has M10x1, then...
I'll check out the links above - thank you for that.