Tuc. Do I take it from your "My opinion is that the responsibility you mention remains with the crew so long as the airworthiness chain is intact" .... means that if the a/c was not airworthy, then the crew were free to ignore the rules of airmanship? Or,? JP
JP: If the crew were in control of the aircraft at the time it entered IMC, (and the last observer to see them before the crash indicates they were at that time in VMC) then they bear a major responsibilty (although due to the criminal lack of airworthiness they may not have been in the position where the aircraft systems led them to believe).
If they were not in control due to one of the many problems demonstrated in testing, on an aircraft described as dangerous by Boscombe Down, then the responsibility lies solely on those who signed documents clearing it for service, and I hope they are publicly shamed.