But were there four rails or only three? At stations there would have to have been only three in order to bring the coach doors close to the platforms, but this would have required a lot of additional pointwork.
There were three rails. Sometimes they changed sides, for example at a platform, using an arrangement similar to points, which meant the signalman had to identify the gauge of the train.
I'm sure I've seen that some broad gauge locos were fitted with wide buffers to enable them to handle both types of stock **. I don't know whether the comment about mixed operation being prohibited was only about double-headed locomotives, rather than wagon haulage, or even where it came from. It's not in the Norton accident report, which one would have thought would be picked up by the inspector. Did Rolt just assume and write it in Red for Danger and it's been passed down since?
Notably the goods was narrow gauge and the boat train was broad gauge, so in the head-on collision the buffers, first point of contact, would not have matched either, and one would have thought would have skewed the trains.
** : Edited to say I've just found a picture of one, titled "Fenton with special buffers for working broad or narrow gauge stock." Here :
If you think about it, there would have been various impracticalities otherwise. The Wellington banker (which the assisting loco in the accident, though detached, was provided for), would need either these special buffers, or there would need to be two bankers provided, one for each gauge, to suit whatever train turned up.
