I have a photograph of my father who I think was in the Royal army service corps, Pioneer corps, Gillespie Squad. He lived in Swansea, South Wales. I have a number which I think is his service number-1759332. I've tried typing this into ancestry records with no result. Does anyone know the best way of finding out what he did and where he served during the war? I know he was in France and Belgium, but that's all