As regards understanding the preceding discussion on Tolerably Safe, I think it all needs to come back to the HSE explanation rather than the defence standard. I also think it is where CAS thinks he got his "safe as it needs to be" line from.
As I've said before, have a read of "Reducing Risks, Protecting People" at
http://www.hse.gov.uk/risk/theory/r2p2.htm particularly paras 122 - 133 and, as regards Tolerable, at para 124:
The zone between the unacceptable and broadly acceptable regions is the tolerable region.
Risks in that region are typical of the risks from activities that people are prepared to
tolerate in order to secure benefits, in the expectation that:
the nature and level of the risks are properly assessed and the results used properly
to determine control measures. The assessment of the risks needs to be based on the
best available scientific evidence and, where evidence is lacking, on the best
available scientific advice;
the residual risks are not unduly high and kept as low as reasonably practicable (the
ALARP principle – see Appendix 3); and
the risks are periodically reviewed to ensure that they still meet the ALARP criteria,
for example, by ascertaining whether further or new control measures need to be
introduced to take into account changes over time, such as new knowledge about the
risk or the availability of new techniques for reducing or eliminating risks.
Spot what is missing from this sad story?
sw