When I was writing the book The London Gunners come to Town I looked in vain for pictures of known soldiers of known units who were stationed in Hemel Hempstead in 1914/5 as part of the 2nd London Division. Well, I'm not quite there yet. This picture was taken by L. L. Christmas, of St Albans, almost certainly early in 1915 and the gun looks very much like a 6 inch howitzer. Unfortunately I can't name any of the clearly identifiable men. (Can you help?)
And who had such weapons in the area at the time. Why the 8th London (Howitzer) Brigade of the Royal Field Artillery - who were based at Apsley, including Shendish. And my research into the book included many details of what the Brigade was doing between August 1914 and March 1915, when they sailed for France.