Here is a picture of the crack on the neck, I can feel this in both directions with my fingernail.
It is possible it is just a score on the tube, but I will look at options to either replace or get another TV if it is the worst case.
There are no outward signs, I would have expected to see such as missing coating on the front, or any getter coating going white, but I suspect that would be under the yoke?
I think I need to apply 6.3 Volts.
Adrian