Sorry, can confirm that's a typo - should read 1337 as per pattern.
Just seems to terminate at Reading.
Apologies, I have misread it. There's two services which are continued in non-adjacent columns and I've mixed them. The 1318 Reading call was the 0920 Manchester to Poole. The 0920 off Liverpool went to Penzance.
Which is actually exactly what the Scottish Region did for the 1982 Basic Interval Timetable on the Edinburgh-Aberdeen route. The introduction of HST differentials allowed significantly accelerated HST schedules on this corridor from May 1982 and the timetable was 'flexed' so that there were different departure minutes off Aberdeen depending if the service was an HST or not. The departure/arrival times at Edinburgh were fixed instead.
Roughly hourly at XX.55 off Birmingham and mostly alternating between either Manchester or Liverpool, though there are a few instances where two in a row serve one destination.
The NE/SW HSTs to the North East are roughly hourly as well at XX.50 off Birmingham.
I think this was the period (which lasted quite a few years, maybe late 70s until early 90s) where the service pattern was hourly NW-SE and hourly NE-SW, timed to cross at New St so that passengers could switch between the two services. The NW services mostly alternated between Manchester and Liverpool, and the NE ones between Leeds and Newcastle but there were a few exceptions such as the daily Leeds-Poole, Liverpool-Penzance, a couple of Manchester-Bristol services and I think there was a single daytime Edinburgh/Glasgow-Bristol, which in later years switched to Poole, and I think for a while ran to Brighton. I remember that the departure times from Leeds were quite variable as they needed to fit into the standard pattern at New St but had very variable stopping patterns - all called at Sheffield and Derby, but some also called at Rotherham, Chesterfield etc. This was in the days when these services all used the old Midland line to Sheffield so didn't stop at Wakefield.