 The episode 's airing on BBC1 gathered 2 @.@ 9 million viewers , 15 % of the audience share , of which 20 % were under 16 . While the film Chitty Chitty Bang Bang , which aired against " Invasion of the Bane " on ITV1 , had a higher overall reach , " Invasion of the Bane " had a slightly higher number of viewers head @-@ to @-@ head . The episode 's audience Appreciation Index was 77 , the average score for an episode of a drama programme . 
