Historical status and road adoption – Castle road, Kingswear

I shall be most grateful if I could be provided with some historical information about the construction of that stretch of Castle road that runs from the junction with Church hill to the point where it becomes private outside the property known as Inverdart cottage.  I assume that this stretch of road was built in Victorian times to bypass Beacon road, which was too narrow to provide adequate access for large country houses then being built further along the coast. Please confirm or otherwise. My specific questions are :-

When was this stretch of Castle road built?

Was it a private construction or by the then Highway Authority – if there was one?

If private, when was it adopted by the Highway Authority?

Why the limit of adoption? Perhaps it was constructed on their land by the owners of the Inverdart estate and ended at the junction with the Brookhill Estate – or it was because the existing road from that point is tortuous and narrow and liable to collapse – or both. 

What was the width of the original road in front of Inverdart cottage before the new road was constructed. If narrower than at present when was the road widened at this point?

Why was the road at this position constructed or widened to a width considerably wider than the rest of the adopted road?

In terms of the historical mapping that we have (publicly available on line through the Devon County Council Environment Viewer: Environmental maps – the stretch of road referred to appears to have been built at some point between circa 1890 and 1905 as it does not appear on the mid-19th century Kingswear Tithe Map, nor on the 1st Edition Ordnance Survey map (c. 1890), but it is on the 2nd Edition Ordnance Survey map (c. 1905).

According to our records the roads and footways coloured brown are recorded as highway maintainable at public expense (HMPE).  We do not hold any other information regarding the building of the road nor when it became HMPE.