Not sure you do. Teesside doesn't have a direct link to London. Eaglescliffe does. The GC service runs up the Durham coast simply because that is the only way the service could get to Sunderland and still have a path south of York which is what GC are really after.
Eaglescliffe station must take no more than 15 to 20 minutes to reach by road from most of Middlesbrough, so I'd say it is pretty clear that Grand Central regards it as serving Teesside south of the river, with Hartlepool performing the same role north of the river.
Huddersfield to Wakefield Westgate is a 35 to 40 minute drive, much the same as the connecting trains, so hardly the same as getting to Eaglescliffe
I wish this board would allow me to use derogatory language! let me be direct: Huddersfield is a dump. It has few enough jobs and precious few of those that would require a regular service to London. People who make good move out. That is why there are more richer people in Airedale wanting to go to London. The same sort of people aren't living in Huddersfield or Halifax. That may be hard to take but it is the truth. It is the same across the north.
It isnt that I like or don't like Huddersfield having a direct train to London. I think it is a complete waste of time and resources and a pointless exercise in PR puffery designed to placate someone rather than offer a meaningful service OR help fix the economic, employment and/ or transport issues that run down northern towns face. I suspect that through customers will be very limited and the vast majority of passengers on the train after Leeds will have got on there.
As an aside i think the same about the Middlesbrough service even though it will benefit me personally. It is a mere sop to buy of the local politicos.
Is there some reason why you keep abusing Huddersfield and and people who live there - or much of the rest of the north as well, it appears - as opposed to the 'persons of higher value' supposedly populating Airedale? Utterly charmless stuff.
You keep claiming a service leaving Huddersfield somewhere around or shortly before 7am and returning most likely in mid-evening would be a waste of resources.
Could you provide some convincing argument as to why this is the case, perhaps starring with what else you would expect a five-car set to be doing at those times of the day to generate vast income for LNER?
Would anyone happen to know whether the majority of passengers - or should that be affluent persons of higher value with all the rights that status apparently bestows on them - currently boarding the Skipton-London service at places between Skipton and Leeds carry on to Kings Cross? I have my doubts...