Evolution of Spooks.

[HarryPearceSpy]

You're right. I could sense a change sometime after series 3. It seemed more action-like and also more of the ends justify the means (as long as the greater good is achieved). There was some of that during the first three series, but afterward, there seemed to be a lot more.

Personally, I mostly liked the changes, although I enjoyed both styles. I also really like how they are willing to tackle so many different contemporary issues (Iran, Libya, etc) during the latter series.