I guess he's the officer in the centre of this photo:
Here's a close-up:
The argument is a bit circular, but hopefully will get clearer as additional information is added ...
Because the group photo has an army officer in the middle, I'm guessing it is a photo of the Garrison School in Hong Kong.
Next I looked through the annual 'REPORT OF THE DIRECTOR OF EDUCATION' documents for mentions of the Garrison School (aka Military School), to see who was writing the report, thinking they would likely be the senior military person in the group photo, i.e. the man in the crop shown above:
- 1912 : no mention of Garrison / Military School
- 1913 : mentioned, but no author given
- 1914-16 : information provided by 'Inspector of Army Schools'
- 1917-18 : mentioned, but no author given
- 1919 : information provided by 'Inspector of Army Schools'
- 1920 : longer report included as Annexe, written by CAPTAIN H. S. MILLS, M.B.E., B.A., Inspector of Educational Training, China, Straits Settlements,
and Ceylon Commands. - 1921 : longer report included as Annexe, written by Inspector of Educational Training, China, Straits Settlements, and Ceylon Commands. No name given.
- 1922: longer report included as Annexe, written by H. H. CLARK, Lieut., A.E.C., Command Educational Officer.
- 1923: longer report included as Annexe, written by A. E. WATTS, Captain, A.E.C., Command Education Officer.
- 1924-25 : no mention
The three bumps on the epaulettes of the man in the photo show that he is a captain. From the list above, that matches either Captain H S Mills in 1920, or Captain A E Watts in 1923. The photo can't have been taken in 1920, as several of the Brownies in the group photo have two stars on their uniforms showing they had been Brownies for two years, and Brownies didn't start in Hong Kong until the 1920s.
So the captain in the photo may be Captain A E Watts.