When Fletcher is telling 4 other prisoners about Warren's letter it can be clearly seen to be addressed, Dear Bunny, however, a little later Fletcher is reading a second letter he is confused about Warren being called Bunny and asks him why but since it was in the first letter why didn't he ask Warren when he read the first letter.
When Fletcher arrive home on leave, the painted backdrop to represent the "street" outside his front door is obviously fake.
Shadow of crew on side of coach as it drives past along the country road.
Fletcher and his wife admit they had pulled this stunt before when he was in Maidstone prison. A simple check of Fletcher's prison file by the governor or Mr McKay at Slade would have revealed it was a trick.