Addison was recently on the RHLSTP discussed the split was amicable most of them had already been contracted for season 5, Iannuccci stepping down to spend more time in Britain with his family after season 4 was a sudden decision and had not been planned for. The rest of the brit writers decided they would stay on…

Yep all the Thick of it contingent left at the end of season 5.
Iannucci stepped down as the showrunner after season 4 but Will Smith, Blackwell, Addison and a few others continued writing and directing for the show. Addison directed at least five episodes of season 5. They all decided not to renew their contracts…

Wholeheartedly agree with this sentiment. It's no coincidence that this is the first season without any of the Brit contingent of "The Thick of It" team who all left at the end of last series (Simon Blackwell, Chris Addison etc.). The show is starting to feel like any other writers room American sitcom some of the…