JP The rules that were broken were the UK Military Airworthiness Regulations, and they were broken long before 2nd June 1994. As tuc reminds us Air Marshals' "form" in that regard can be traced back as far as 1987. That is the focus of attention now, not the alleged breaking of "the Rules of Airmanship".
BTW JP could you please point me to the "Rules of Airmanship". I always thought that airmanship was a philosophy of best aviation practice rather than a set of prescribed rules like....well the UK Military Airworthiness Regulations for example.