Ironically, The original LNER (roughly what is ECML today plus all its branches and Scottish east side) was one of the big four private railways companies formed after the First World War by consolidation in the 1921 Railway Act! It was the second largest after LMS (roughly what is the WCML plus all its branches and Scottish west side)
Anyway, here is the new website of LNER....
The big four companies were in poor financial health, both due to incipient competition from the roads and more importantly to general poor state of repair caused by WW2. The government at the time saw nationalization as the way out of this problem.
LNER management however had a different proposal and petitioned the government to consider a franchise system under which the government would buy the tracks and the big four companies would be able to compete for franchises to run services. Basically they wanted the system that exists in the UK today.
The government would hear nothing of it. This was the same government that introduced free healthcare, nationalized a whole bunch of industries and introduced other Scandinavian style soft socialist policies and so weren't open to mixed private / pulic models for running public services. But it is interesting to think that if things had turned out differently, history might have taken a wholly different course, with consequences that we can only guess, maybe positive, maybe negative.