37204 passes Marshfield on Saturday 28 April 1984. As this doesn't remotely match up with anything in the working timetable, I can only assume that it is either a special, or a late running 6V64 02:10 Albion to Waterston Gulf oil empties. The other alternative is an extremely late running 7V89 22:23 Tonbridge or 01:45 Redhill to Llandarcy. In either case it must have picked up the train at either Severn Tunnel Junction or Newport, as the loco passed by light engine in the other direction just over an hour earlier.