A club member recently acquired a large British car of the better class [but it was not a Jaguar]. Driving it home some considerable distance, like from Victoria he had an electrical problem in that the Lucas generator stopped working. Parts were hard to get but he soldiered on by buying a spare battery and charger and only driving by day and charging batteries overnight.
The upshot was that there was nothing really wrong with the generator except the brushes were totally worn out and he found that by applying light pressure to the brush springs he could get the generator "on line".
A trip to see Kevin Baker the Lucas guru who lives at Maleny [ph 5494 4221] netted a set of brushes for one of the largest generators you will ever see in a car and the problem is fixed.
However I wonder how many of us are driving around with worn generator brushes. Unscrewing the clamp on the generator cover and simply looking at the top of the brush holder and spring easily inspect them. If the brush is well down in the holder its time to get in touch with Kevin.