snaga
Dealing with your last point first, the lack of clarity. I agree, or we wouldn't be having this discussion. I made the point twice earlier, The CAA/NATS/MIL/Home Office/Police and all the other bits that hang on and get involved SHOULD sit down and explain why they do what. It may not help these situations, but at least everyone knows then why things are done.
Ok, having established that, dealing with the 'who's in charge' point. This isn't a peeing contest. The pilot knows how to fly and operate his aircraft, as a Police officer, I am not interested in that, nor do did I want to get involved in it. But where I do did get involved is when it arrived at the airport I worked on. From that point, its is as I said the responsibility of the senior police officer on scene, be that a PC or the Commissioner.The reasons it is isn't up for debate, its in a home office memo. Even if you ignore the T word, the aircarft, in both circumstances are scenes of crime, and again, fall under police control.
Now, usually, the deicisions are made by 'committee' at this sort of thing. The captain is the planes expert, Police are the terrorism experts. The Airport authority provide the faciliies and so on. It works provided everyone understands why. In these 2 cases, that has either broken down somewhere, or there were reasons not to say. I can't say which, I wasn't there.
You should not assume that because you can't or don't agree with what is from Police point of view a valid reason for not doing something, then they are wrong. They had more info that you do on the subject.
It could also be of course that the airline had decided the threat was green, and therefore there was no need to evacuate. We don't know.,