(14 Nov 2021, 11:20 am)Andreos1 wrote Which means naff all in the grand scheme of things, when the 71 is stand-alone and could easily have its timetable tweaked to improve its headway with the 78.

The 35 fits around the 8, which fits around the 78 (no major timetable changes with the latter for many a year if I remember correctly - always a quarter to and quarter past from Park Lane with the 638 being bottom of the hour and 777 top of the hour). 
Absolutely nothing to do with the 71 running. That's just poor planning. Or not?

The 71 is a complete red herring in this instance as the cycle time of the 71 doing Chester-Seaham-Chester (120 mins). So a nice round number. But it's out of sync with the 78 doing Chester-Sunderland-Chester (92mins without layover at Chester) So you'd have to change the 78 timetable and everything else that may interfere with it fit the 71 in better.