Lonewolf 50, I'm not saying why these two aircraft collided because I don't know. What I am querying is why the operator was so sure that it was not because both their fwd HISLs were switched off. As tuc rightly points out all the other holes in the cheese slices meant that this compromised their last line of defence. As to both calling visual, visual with what? You mentioned a smoking gun, might that not have been the Lynx?
I don't expect anyone to know why these aircraft collided, and if they say they do I would suspect an agenda of some sort. My point all along is that, in common with all other Military Air Accident investigations to date, this was investigated under the auspices of the operator. That does not make for objective conclusions on which one can build in order to avoid avoidable accidents. That is the whole point of Aircraft Accident Investigation.
In the meantime a question mark hangs over this tragedy. One thing we do know though is that the HISLs had been fitted in contravention of the Airworthiness Regulations and had not been subject to trials, as well as other LRU discrepancies mentioned by Dervish . That is why it remains an Airworthiness Related Accident.