There is almost no history of direct trains between Cambridge and "the north". When I was growing up in Cambridge in the 1970s the farthest north it was possible to go from Cambridge on a direct train was the summer Sunday train to Skegness.
Quite. I'm not sure that Cambridge would be the better off if the former Colchester-Barrow-in-Furness service were resurrected
The nearest to an exception is the Sprinter 1.0 timetable introduced in 1988, which did include a few trains to and from Liverpool.
What are the reasons EMR's Liverpool-Norwich train goes to Norwich and not Cambridge? If I had to guess it's a combination of lack of paths, service would be overwhelmed and the need to provide something fast/more capacity for Ely-Norwich.
You might equally well ask why the XC service goes to Cambridge rather than Norwich! Ultimately, they overlap, and (from experience) the EMR service is far from rapid
But that only lasted until 1994, when the service was split into Norwich-Liverpool and Cambridge-Birmingham in advance of privatisation. That was set in stone when the Central Trains franchise was broken up, putting Norwich-Liverpool into East Midlands and Cambridge-Birmingham into Cross Country. Of course that was all before Cambridge started to grow rapidly.
The solution to Cambridge's connectivity to the north is coordinated interchanges at Ely and Peterborough. Adding additional trains on top of what already operates on the Ely-Peterborough line or the ECML would be (probably prohibitively) expensive.
A second/new tph to P'boro would be a modest but big help here, whether they go on to Birmingham (that route through Stamford etc needs more service too) - or as a shuttle.
All of Edinburgh, York, Leeds and Nottingham have bigger flows from Cambridge than Leicester. For connectivity with "the north" what Cambridge needs most is 2tph Cambridge-Peterborough, for ECML connections, and that would be a big benefit for local journeys too. One of the most absurd features of the current arrangements is that the first train from Peterborough does not arrive in Cambridge until 0814, and the last departure from Cambridge to Peterborough is at 2100, which is horrendous for local connectivity.
As you say, the solution is better interchanges, but Peterborough isn't going to be rebuilt with cross platform interchanges and coincidental always on time changes.
Peterborough has already been rebuilt twice in my lifetime.
I'd imagine the Ely area capacity enhancement (EACE) would need to be completed before anything meaningful could be done. Is that still on hold?
This is a classic example of "something must be done, this is something, therefore we must do this". EACE did nothing for Cambridge apart from 2tph on the Fen Line, and that's mostly been achieved already, with a bit of investment in platform extensions.
From a Cambridge perspective, East West Rail remains the priority, and I'm not optimistic that Cambridge will get much from central government on top of that, because they want growth in postcodes other than CB too. Anything else for Cambridge is going to need local and/or private sector funding.
But that doesn't mean that nothing can be done. GBR has already given us the Greater Anglia business unit and the new rolling stock and infrastructure strategy. For what its worth, my preferred way forward is electric/battery bimodes (something like the recent Trans Pennine order?) to operate Stansted-Norwich/Nottingham, and class 170s Norwich-Birmingham, both operated by Greater Anglia.
