Gentlemen,
nice to see that the vitriol has now died down, and some thoughtful responses are now being offered.
I agree with both sides of the arguement, neither one of us is perfect and we both need the other to do our job properly. Teamwork...
I can't remember who mentioned earlier about not having heard of an incident being due to someone busting a level?
My immediate thought was northern India about 3 years ago...Saudi and a Russian. The Russian busted his level and collided with the Saudi.
TCAS could have saved the day...but if I remember correctly, the other aircraft wasn't squawking, so the Saudi had no warning of it. I may be mistaken, but I think you get the idea.
In this part of the world, it seems very regular that some airlines(?) refuse to turn their transponder on until required to do so.
Sad but true I'm afraid.
I had an aircraft rightly screaming at me about a 100m near miss that he had over the Indian Ocean, not in my airspace I hasten to add...that one didn't have his transponder on either! The first he noticed was a very big blue and white Russian in his window!
BTW, I'm not sure of the system that you guys have in the UK, but here we can "tag" a primary return with a label...the only thing it doesn't give out is a height readout, so for the pilots out there, you may not see it on the TCAS as it doesn't have a transponder, but it could well be out there.