TUC, "At the time, legal advice was 'the clock runs on litigation from now', '
Not sure on this. If ear protection for engine noise for instance was not issued then people serving at that time, is pre-74 were highly susceptible to high tone deafness. It was certainly known.
From 1978 improved protection was available, but was it effective? Did everyone have it?
From about 1990 wearing such protection was enforced, but again, was it effective?
Simply setting a date does not address the issue of those already exposed compared with those who subsequently did not use the kit provided.