Low and Slow, It is very difficult, but not impossible to show gross negligence without CVR and ADR. Many years ago (70's I think), a Lightning pilot decided to give an impromptu flying display off the Yorkshire coast. He flew into the sea. The display and crash were witnessed by hundreds of onlookers. He was not authorised for a display nor was he supposed to be off the Yorkshire coast at the time. Regardless of other factors, he was clearly negligent. Not particularly relevant to this case, our boys were authorised for the sortie, and there are no direct witnesses to the crash. If a skilled observer or flight survivor had witnessed the final few seconds of flight it may have been possible to show negligence without recourse to a CVR and ADR or pilots testimony. This is not the case therefore there must be significant doubt.