“I agree with the Secretary of State that the words “follow the route must be taken to have been adopted advisedly; that “route” refers to (in the broad sense) the pathway to somewhere and that to follow has connotations of keeping to such a pathway. I accept the submission that the deliberate use of the words “follow” and “route” focuses us upon the claimant’s ability to navigate along pathways and is not concerned with other possible problems that a claimant may have when being in the natural environment.”