............that the outer leaf of bricks has been built up between each
truss so
that it comes right up to the roofing felt. An even more effective
block to any ventilation. Is this normal practice? ..........

Just the same in my bungalow 1950's and seen it done often in various
houses.
Sure would be a hell of a job for me, shifting all those bricks.
As for normal practice, well that seems to change over time.
I bet at least half the building regulations at present will be scoffed at
in ten years time.

If it's such a bad idea to brick up to the felt all round the roof space
now,
why was it OK in 1952.?
Must be different damp