 Equally important in terms of traffic but not as extensive in terms of route were the running power agreements with the Midland Railway ( MR ) . For the NSR passenger traffic into Derby and Burton was authorised and good traffic as far afield as Wellingborough . The arrangements with these two companies allowed the NSR to run its longest passenger service , between Derby and Llandudno . These trains only ran 44 @.@ 5 miles ( 71 @.@ 6 km ) on NSR rails , with 6 @.@ 5 miles ( 10 @.@ 5 km ) over MR but with the majority , 67 @.@ 5 miles ( 108 @.@ 6 km ) over the LNWR . 
