Erm, so, lockable cockpit doors. Being a natural conspiracy theorist, why did the FO let the deadheading Captain into the Flight Deck if he felt there was something amiss? I think I'd keep the door locked and land it myself once I felt I'd reduced the threat I was facing.
That, to me, probably confirms the pointlessness of lockable cockpit doors.
And I liked the comment above about is the armed pilot program still in place! It is as far as I'm aware; could have been a very different result if he had been.
I await the next knee jerk security overreaction with baited breath.