Can a benefit giro be cashed at any post office?

My alcoholic father-in-law is coming to stay with us today; he lives in Derby and we live in Swindon. He has a giro that needs cashing and are wondering if he is able to cash it at our local post office or if he will need to use his regular one? If he can do it here in Swindon, what form of ID wil he need? Thanks in advance.