Spot on - although was it the Teign Valley Line - I though that was the loop from Exeter to Newton Abbot via Heathfield, with the line to Mortenhampstead a branch off it?
Actually, yes. Though historically the Moretonhampstead and South Devon Railway was first, with the Teign Valley line branching off at Heathfield, inevitably the remaining branch came to be seen as secondary.
I was surprised to find that that bridge was not "borrowed", but newly built for the Wray Valley (Cycle) Trail in 2010/11. There's another new bridge over the A382, this one on a new alignment, just down the road. I think there's still more of the trail to be built, though (apart from the usual financial issues) the fact the Dawnus was one of the main contractors won't help.