Why? Linking Tavistock and Okehampton by rail, as distinct from having them as branch line termini, can only be justified if there is an adequate business case, which as others have argued on this thread, is highly unlikely. Such a case can only be based on local benefits for these 2 small towns - it would be too roundabout as a through route from Exeter to Plymouth, and have long stretches of single track. As Okehampton looks towards Exeter and Tavistock towards Plymouth as the nearest major cities, these benefits are likely to be sparse.