It's a tiny picture, fade and worn as you'd expect for a piece of paper it's age. I was looking to squeeze a little more information out of it, it was found with a rather colourful Poem to my grandmother dated 1919 but I'm not confident enough to say this was taken during WW1. I was hoping for a confirmation of a rough date and perhaps the place where this was taken. He didn't leave many artifacts from the war behind, just a cap inscribed 'Sgt. Cross' that still has it's Manchester Regiment Fluer De Lis on the front.
I never knew the man, he survived the war but died before I was born, my relatives know about as much as I do. It would be nice to a get a miniscule glimpse into his life especially on a day like today. Cheers.
No idea of the location, but for timeframe he appears to be wearing the uniform of a WW2 British Expeditionary Force infantryman, so 1939-1940.
The boots are bloused and his trousers have pockets on the front leg.
http://www.sofmilitary.co.uk/ww2-1939-bef-uniform-set-product,14446
I'd suggest posting your photo in https://www.reddit.com/r/whereisthis/. I bet somebody there could identify that building in the far distance.