Probably Kings Liverpool Regiment [KLR], Officially the 'King's Regiment' , https://www.google.com/search?channel=trow2&client=firefox-b-d&q=liverpool+regiments, badge on the young man looks about right, however the Cap badge on the older [Officer] seems indicative of a Fusilier or Grenadier; may have transferred? http://guttedarcades.blogspot.com/2012/05/bears-paw-restaurant.html - Located at 53 Lord Street in the Bear’s Paw Building. Managed by James Cottle Limited in 1927. Destroyed in the WW2 by German bombing. Hope this helps.
Hi Jane. The reunion autograph card shows the card owner to be an H. Mackie. Is this your Grand? If so a brief search of the Medals Card Index for WW1 throws up a 2/Lt Holm Andrew Mackie, Royal Scots Fusiliers. He may have started out with the KLR and later accepted a promotion with the Fusiliers, explaining the change of cap badge. Hope this helps you. Buster.