Mallaig Extension Railway 
Does the Mallaig Extension Railway really qualify as a "Historical Railway", given that:

 it's still open from end to end, and
 it's actually of quite recent origin, relatively speaking?

 

I think it does. Having worked along the C&OR; and up the WHL to Fort William; Banavie Peir came to mind; and the Invergarry and For Augustus Railway. For completeness I felt it is relevant. Linking into the NBR and then onto the LNER - detail still to be added. Loch Eil Outward Bound is a station that is not included. The West Highland Railway is another issue that need thought - for the same reason.