Officer Training Battalion, 1918

[KOSB1918]

Hi Folks,
Can anyone please help with information about Officer Training Battalions of WW1?
I have a photo taken in the first half of 1918 showing a group of officer cadets in an Officer Training Battalion. My grandfather, James Simpson, is standing fourth from the right.
Dating the photo was fairly simple - several officers are wearing Overseas Service chevrons which came into being in early 1918, and my grandfather was commissioned to the King's Own Scottish Borderers on 26th June, 1918.
The officer standing third from the right is wearing a cap with a cap badge that seems to be casting a shadow. Is anyone able to identify the cap badge, or see anything in the background or elsewhere in the photo that might identify the location?
If it is any help, before being commissioned my grandfather had previously served on the Western Front as a Sergeant/WO2 with the Argyll and Sutherland Highlanders.
Thanks very much for reading this.