I've merged the four threads on this series into one.
I watched the first season of this, and maybe the second. I can't remember now, but I think all the main characters died in an explosion or shoot out, and I somehow never got involved in it again.
Many people have told me what a good series it still is, and I was just reading some reviews about it. The producers put part of its success down to their uncanny ability to predict the future - they had a plot where terrorists planted bombs on London buses which aired just shortly before the London bombings - they had a plot where London came to a standstill because of the security surrounding the visit of a foreign head of state which aired just shortly before London came to a standstill because of the security around the visit of George W Bush. There were other examples as well, but I forget them.
Another reviewer commented on how they continue to kill off major characters on an almost weekly basis. I like the idea of a series being confident to do that. It must be realistic of someone actually working in that kind of job, but I can't see it keeps viewers watching the show.