In my day the Rules of Procedure for BoIs, laid down in MAFL and QRs, were aimed at a "quick and dirty" exposure of causes of an accident, allocation of blame, and recommendations for a "quick fix". They played merry hell with the normal rules of evidence applied elsewhere in the courts. "Heresay" was admissible, witnesses could be compelled to answer possibly incriminating questions etc, etc. In recognition of this, evidence at BoIs could not be used in any subsequent legal action . The proceedings were usually classified Confidential under the OSA, and so untested evidence could not be used by the media to impugn the characters of witnesses. To the best of my knowledge the findings of the BoI on the Heathrow Vulcan tragedy have never been released. I think that was a healthy state of affairs and regret that it has been allowed to lapse.