My grandfather in the back seat apparently.
It is a British Airco DH9A light bomber.
Some more info: According to an RAF database, this particular aircraft with registration E848 served in RAF No. 27 and No. 30 squadrons. Both of these squadrons flew sorties over India and the Middle East after World War I (hence the additional radiator fitted under the fuselage to operate in warmer climates, well spotted by Peter Kämpf), but I can't find anything more specific about E848 that would place it in either squadron in particular at any specific point in history.
2$\begingroup$ Light is the word for it. $\endgroup$ Nov 3, 2016 at 17:28
2$\begingroup$ Minor detail: It has the additional radiator fitted under the fuselage to operate in the Middle East in the 1920s (in a particularly shameful episode of British warfare). $\endgroup$ Nov 4, 2016 at 16:52
$\begingroup$ @PeterKämpf Wow, well spotted! You've motivated me to try to find out a bit more about the history of this particular aircraft ... $\endgroup$– CooperNov 4, 2016 at 17:28
$\begingroup$ @PeterKämpf: Would that be the one where the RAF bombed the Kurds with mustard gas? $\endgroup$– VikkiMay 25, 2018 at 1:12