All Available Season All Season Specials Apr, 2007 2 episodes 0.0 Series 1 Apr, 2008 3 episodes 6.8 Series 2 May, 2009 4 episodes 6.5 Series 3 Sep, 2010 2 episodes 5.5 Series 4 Sep, 2011 2 episodes 6.6 Series 5 Aug, 2012 4 episodes 7.2 Series 6 Feb, 2014 4 episodes 7.1 Series 7 Apr, 2015 4 episodes 3.0 Series 8 May, 2017 2 episodes 1.0
