Tandemrotor
As you are probably aware, it is the duty of the President of the BOI to issue a signal WITHIN 48 hours of an Accident giving the BOI's initial findings and any subsequent recommendation regarding airworthyness.
I happen to know (because I asked the question) that during my relatively short RAF career there were 764 "accidents" (including motorised gliders). If the RAF grounded the fleet every time an accident occurred the the RAF would never get airborne.
The finding of negligence in the Mull accident was because the Pilots were attempting to fly VFR in weather conditions that (in the words of the BOI) "required flght in accordance with IFR in the vicinity of the Mull of Kintyre".
Incidentally, I put "accidents" in inverted comma's because the definition has changed over the years.