Over the years I've made trips to Scotland by rail to both Edinburgh and Glasgow Central.
One thing that puzzled me was from Kings Cross the is pretty much a half hourly service yet the Euston to Glasgow Central appear to be be mainly hourly.
Is there a reason for that ?
Edinburgh is 392 miles approx.
Glasgow is 400 miles approx.
So it can't be because of mileage.
So how come Glasgow is only one per hour ?
The northern ECML gets 3tph to Edinburgh, 2 from London and the XC from Birmingham/EMids/Yorks.
The northern WCML also gets 3tph to Carstairs, 2 from London (one via Birmingham) and the TPE from Manchester/Liverpool.
The WCML Birmingham and TPE services alternate between Glasgow and Edinburgh.
The NR view is that the WCML hasn't got the capacity for extra services, mainly because of the freight provision which doesn't apply to the same extent on the ECML.
Historically, the ECML route was preferred to Edinburgh and the WCML route to Glasgow, though both could and did service the other destination.
In fact, the WCML could provide the main Edinburgh service if desired in similar journey times to the ECML, and was planned to for HS2b (with combined trains dividing at Carlisle).
During BR times, the WCML lost its primacy for beyond Glasgow services (to Perth/Aberdeen/Inverness), because of the closure of the Forfar route and diversion of through services via Edinburgh rather than Coatbridge.
Virgin/Avanti were also not interested in running services beyond Glasgow/Edinburgh, and serve Edinburgh only indirectly via Birmingham.
The ECML now has the direct Stirling/Perth/Inverness service whereas until the HST era this was a WCML service.
With non-tilt bi-modes all the rage, there is nothing stopping those services going back to to the WCML one day.