One day about 20 years ago. or possibly a little more, I saw a Class 33/1 with a 4TC set in all over blue livery in the old Platform 4 at Reading station. The station announcer was on the PA saying the train was for "Clapham Junction and London Waterloo only". This was at 09.00 on a weekday, and the train was not a special. I just wondered whether anyone knows anything more about this unusual working. The Reading - Waterloo service was invariably an emu with numerous stops on the Southern route, but was there a particular reason for this apparent diversion? Was there a diversion via the GW main line and the West London line to Clapham, or did it run nonstop along the SR route? Any info would be greatly appreciated.