Manipulating the Government/Political System

[Silktie]

You're right, there is definitely a strong element of that. I think they are trying to establish through this that the team, and Harry in particular, is not fond of politicians in general and that he would go against the government if they are planning morally questionable activities. However, I feel that the writers are not consistent on this aspect, as there had been times when Harry followed pretty horrendous orders from the Home Secretary, as seen with the bomb in Tehran in season 6. Perhaps as long as he believes it to be in the interests of the realm heis willing todo pretty much anything.

On the other hand, how many times have we seen the politicians working against MI5? Oliver Mace is a case in point,

Spoiler: show

as well as in season 6 when the Home Secretary actually orders the team's assassination.

So in the end we get the idea that both sides (MI5 vs politicians) are tolerating the other as a necessary evil.