Shell Management, we have crossed paths before on other threads but your comments here really do exceed even your own wild standards. That operators have not submitted a safety case to the Authority for operations in high ash concentrations is certainly, in my employer's case, due to the fact that we do not believe that the risk can be acceptably mitigated. I find your armchair "judge and jury" attitude that this somehow represents a failing on the part of the UK industry to be gratuitously offensive.
In any case, how do you define "high"? "High" concentration would be anything more than 4000 micrograms per cubic metre - and potentially with no upper limit. You could conceivably fly right through the plume of a volcano if you had that approval. I would hope that even you would agree, in light of the BA and KLM 747 experiences, that such activity is not advisable.