Maintenance
As long as aircraft, or anything else for that matter, have required maintenance operations to be performed there have been and will continue to be unintended consequences regardless of where or by whom the maintenance is performed. If, as has been suggested by another superlame, the leak was from an area disturbed during the recent IP/HP bearing cavity boroscope inspections then it may have been done by Qantas engineering staff. Depends where the aircraft was at the time the A380's were grounded. In any event, as good as Qantas engineering is/was, nobody is infallible and "murphy's law" is alive and well. As for the discussions as to whether or not the flight should have continued it would be well to remember that the Captain who was there and not in some loungechair determined that it was safe to continue to LHR, a decision which proved to be a correct one.