I would say that he is a post war Regular soldier. the standard of turnout, the presence of metal BERKSHIRE shoulder titles and the collar badges are the clues.
If he was early war TF then he would have TF titles- late war would be cloth titles and mid- 1919 would probably still be slip-on cloth.
Collar badge wear was a bit haphazard before 1914 and during the war; but standard for post 1920.
