The pre-Grouping companies were fiercely competitive and would defend any incursion by another company penetrating what they considered to be their 'territories'. Nevertheless, at times they would co-operate. This co-operation resulted in a large number of joint lines. These joint lines ranged from fully independent operations, complete with their own staffs, locomotives and rolling stock, to short lengths of railway used by the joint companies, with the cost of maintenance shared.

There were more than seventy of these joint lines and all feature in this series by popular railway author Patrick Bennett. This volume focuses on those found in Scotland and the north of England.