The vision that a portion of the train could just be uncoupled and then run of its own accord into the station is today unparalleled. Here is a great period video explaining the whole operation at Bicester. My favourite moment? It's the cheery wave from the train guard out of the window as the slip coach is detached and slows.
So how did the passengers know to get into the right portion? And if they wandered off or went to the buffet, how were they all gathered up before the guard pulled the lever. And to someone like me who enjoys fiddling, how did you prevent small boys playing with the lever?
How is this relevant to the WSR? Slip portions were dropped at Taunton and hauled to Minehead. There is a picture somewhere. I'll try and find it!