OG, because the Post Office have no idea if the person drawing is a trusted rep or any old person. When I worked in the NHS and we were getting people ready to go home, we used to come accross this problem with people who needed cash in the era of pension books. We got over it by documenting it in the patient notes and getting the patient to sign it and then by two members of staff doing the whole transaction. It was actually easier for us if the person had a pension book as there was no issue with knowing a person's pin.