Granddad Elsdon. Auxiliary Fire Service

This is a picture of my paternal grandfather, George Henry Elsdon. He was a plumber by trade but at this point was the caretaker at the Middle Temple in London. My Dad wonders if this was taken on the roof. I think it says "AFS" on his breast. I suppose this photo would therefore be c.1939 - June 1942, as he joined the Royal Marines after this date. Unfortunately, I have not heard any stories about his time with the AFS.