Nick ... I assume you have never served in a military organisation, and also that you are not legally trained.... if I'm wrong in either case I apologise.
The Sgt pleaded guilty, at a Courts Martial that is the end of the affair EXCEPT for mitigation. The Judge Advocate has to comply with the pre-existing sentencing guidlines unless he feels the mitigation is strong enough. In this case he didn't.
Now I wasn't in court, so I can ONLY go by what is reported, however much of that does not "ring true" to my "military" ears .....
It is "claimed" that since his "coma" he suffered a memory loss ..... question .. if that were so just how is he still a serving member of the SAS ?? with all the security and stress that such a position holds ?? Sorry .. IMHO (and I could well be wrong) that is a nonsense....
As a fully trained and operative member of the SAS he has (had ?) more training and knowledge of weapons handling rules, regulations and prohibitions, than probably any other serving members.....
He knew the rules, especially as a Sgt and Platoon Leader where he is supposed to set an example, but broke them .. big time ... and is now paying the penalty ....