Well a bit more digging before Breakfast:
Leete's Moth at Bushire, Persia late December 1926. The Moths stopped at Bushire for six days to overhaul their engines. Stack is pictured second left between Sir Samuel and Lady Hoare. Looking at his hair cut he is probably the suited gent in the mystery photograph. Others in the image include Captain Leete and AVM Salmond. Obviously this is not the Moth in the mystery photograph.. Photo and info credit Aviation Postcard Club.
This is Stack's DH Moth unusual at the time as it was painted white to reflect the heat of the Indian Subcontinent - almost certainly the 'Mystery Moth' thus dating the first image to 1926.