Here's a 1962 timetable for the line, showing among other things the Pines Express, though with no indication of which route it took. There would be quite a lot of diesel by then.
http://timetableworld.com/image_viewer.php?id=2§ion_id=49
And while there, here is a 1949 Western Region timetable, clearly of GWR origins, which shows the overnight mail to the Cambrian line ran via the Whitchurch-Welshpool line (well it would, keeping it on the GWR as much as possible), and on Sunday mornings it was the only train on that line. What a nuisance and expense to have to open up all those signalboxes for just that one train in the small hours. In avoiding Shrewsbury, that town was obviously not the mail consolidation point for mid-Wales that it later became.
http://timetableworld.com/image_viewer.php?id=5§ion_id=1410
http://timetableworld.com/image_viewer.php?id=2§ion_id=49
And while there, here is a 1949 Western Region timetable, clearly of GWR origins, which shows the overnight mail to the Cambrian line ran via the Whitchurch-Welshpool line (well it would, keeping it on the GWR as much as possible), and on Sunday mornings it was the only train on that line. What a nuisance and expense to have to open up all those signalboxes for just that one train in the small hours. In avoiding Shrewsbury, that town was obviously not the mail consolidation point for mid-Wales that it later became.
http://timetableworld.com/image_viewer.php?id=5§ion_id=1410