If you know about the footpath (thanks Alan for the piccy) ...
Asking Traveline for a journey via Marston Green ...
It all goes to show that "official" journey planners do not always give the best option. If it were available (correspondent Alan or his equivalent at the end of the line?), a local phone number would be better.
A comment writer made a likely suggestion ...
National Grid’s role is to connect the railway with the national electricity network. One of the locations where this needs to be done is Melksham.
The Melksham site
To make the connection in Melksham, we will use 25kV underground cables to carry the electricity. Two lines of cables will run from the existing National Grid substation off Westlands Lane and connect to the railway further north at Thingley Junction.
Building the connection
The connection will take around a year to install and work will be carried out in sections. The cables will be laid down into trenches within a working area about 20m wide. To go under streams along the route, the cables will be drilled horizontally underground as a small tunnel, rather than laid into trenches. When the work is complete, we’ll return the land to how it looked before.
It still seems daft not to plod on to Bristol!