Hi there. I am new to the forum and was wondering if anyone out there could help me find an answer to this puzzling question. I have been doing some research into my family tree. When checking out my grandfather's military record from the First World War, I found out he had two service numbers. He is down as Private No 1569, London Regiment, and also Lance Corporal No 25227, Machine Gun Corps. I know he started off in the London Regiment and then moved to the Machine Gun Corps. But why the change of service Number? If anyone out there knows why two different service numbers would have been issued, I would be most grateful for the info. Thanks. Martin.