Can someone identify the regiment my great grandfather served in during the war?

by Jetrox

Sorry, not entirely sure if this is the right sub. My grandfather is trying to figure out what regiment his father served in based on this photo.

http://imgur.com/gallery/Us9IiAn

Was wondering if anyone could help identify based on the hat or uniform? And if not, where I could find more information.

Much appreciated

BRIStoneman

Hello! The distinctive forage cap tartan suggests that he served in The Royal Scots, also known as the Lothian Regiment, as seen here. Unfortunately, I can't say more about which specific battalion.