Thanks to this thread I discover I'm hazy about where the national rail system ends in that part of the world and where the heritage rail begins.
Well .... it's complicated. While the the train derailed on top of the crossover that links the two railways (but not because of the points), the whole crossover is Network Rail's. They also own/are responsible for a short stretch of the DSR's route (the Down Torbay) including the crossover and the level crossing (so they have the whole of both). Consequently DSR have running powers over that six chains or so!
Looking at Google earth there is a catch point there and probably what failed. The view also show the shocking state of the network rail side compared with the Dartmouth Steam Railway
I can barely see that on the satellite picture, even knowing exactly where it is now - so you're doing well if you spotted it there. It's clearer if you zoom in on the Street View from the bridge (further than Google can). The catch point is also marked on Traksy.
Looking at
the pictures on Railforums, the outer rail has come apart at the joint just after the catch point. So it looks more like that failure was the cause, though none of the track there is in impressive condition. Note this is well before the trailing point of the crossover; roughly opposite the point on the Down side.
Click on the map to explore geographics
