I finished up at the top of Mach 3 on the last day of the trans cambrian ride. I was a bit confused by a "footpath only" sign at the top of the last descent. I've just checked the OS map and it's a dot-dash line, aka restricted byway. So it's not "footpath only".
Have there been issues with locals objection to cycle traffic? Quite a few signs seemed to be missing too.