If the bolts / nuts had been required to be secured using some kind of wire locking ,or similarly retentive ,device,as is the standard procedure in aircraft maintenance, then A) they would not have worked loose, B) their abscence would have instantly indicated either sabotage or negligence.The latter could easily be established by checking a written logbook containing the signature of the person doing the work. But it is all rather academic really, as nobody ever gets the blame, nobody ever gets the sack, nobody is ever accountable or responsible ( like our MPs & Ministers,) so what"s all the fuss ?? It"s happened before, and it will happen again !! And again .It"s the British Way !!!