Your local county council (not the district one), or your unitary authority (as appropriate) will hold the 'Definitive Maps', showing where public footpaths are located. That will show whether the route has been officially recorded as a public footpath.
If the path is not on the Definitive Map, you can apply for it to be added. There is no charge for making the application. If no challenge has been made to the public using the route, for a period of 20 years, the council will be obliged to add the path to the map:
http://www.ramblers.o...recorded_right_of_way
Once a path is on the Definitive Map, the council would have to make a Path Order in order to close it. The process is akin to a planning application, in that public consultation is mandatory:
http://www.ramblers.o...mment_on_a_path_order
Chris