My grandfather is in the middle row. He joined the RAF as a boy entrant in 1920. He served in Iraq 1924-27 and India 1927-29 so I suspect by the uniforms this is from one of those postings.
I believe the plane is an Airco DH-9A.
The location may be Iraq. It looks like the RAF 55(B) Squadron: https://en.wikipedia.org/wiki/No._55_Squadron_RAF#Between_the_Wars.
On another picture I think I recognise the dog on the right in your picture (but now a bit older): https://55bomber.wordpress.com/2010/12/02/raf-55b-squadron-hinaidi-iraq/
$\begingroup$ Wow, that was almost simultaneous :-) $\endgroup$ Jan 17, 2020 at 18:54
$\begingroup$ @CamilleGoudeseune I undeleted my answer after adding stuff on the likely(?) squadron. But I do recognise you were first on the plane. $\endgroup$ Jan 17, 2020 at 19:36
6$\begingroup$ Clever to exploit the dog. I got nowhere looking for its triangular insignia. $\endgroup$ Jan 17, 2020 at 19:44
3$\begingroup$ What about the other dog? :-) $\endgroup$ Jan 19, 2020 at 12:38
$\begingroup$ @CJDennis didn't even see the black dog! :O Maybe the rapid movement of the white dog drew my attention. $\endgroup$– gsamarasJan 19, 2020 at 13:50
Airco DH.9A. It served during 1920-1931 in the Middle East and India.
Same prop, prop hub, radiator, wing struts, dihedral, exhaust stacks.
I couldn't identify the thing hanging from the top right wing. Wikipedia's photo has something else hanging there, shaped more like a tiny dinghy than a fuel tank.
I couldn't identify the "triangular roundel" on the radiator, but it matches the one on the side of the nose and on the wing bottom, in Wikipedia's photo. It may indicate a theatre of operations.
1$\begingroup$ I had the same answer but 1 minute later. I concur. :) However, now you also have to provide the location! $\endgroup$ Jan 17, 2020 at 18:56
$\begingroup$ BTW, Wikipedia's first picture shows that same thing hanging from the top wing to the right of the pilot (his right). Whatever it is. Your picture does not. And that triangle sign (in a different location). $\endgroup$ Jan 17, 2020 at 19:10
1$\begingroup$ Location: in front of a hangar! Maybe someone who knows military uniforms (or even names to match to faces) could figure out which airbase this was, and when. $\endgroup$ Jan 17, 2020 at 19:11
3$\begingroup$ Thanks all, and top work on the dog identification! My grandfathers service record shows he was with "M Sqdn" Iraq, then 55 Sqdn Iraq so spot on guys, thank you. $\endgroup$– tim091Jan 18, 2020 at 8:03