Hi Roy and welcome to Rootschat,
Both images would be from the 1st ww period and although there is nothing that I can see that would say which regiment the first soldier served with the second does give some clues. The sergeant on the left appears to have been serving with the Kings Regiment when this was taken, a high res' image of just his cap badge may confirm this, but I am always open to be corrected. If you were to place a link on the armed forces board, or if a mod would move it over to there for you, you may get more answers and help.
What was his name by the way.
OR.