Theroux's 'Paedophiles' attracts 2.4m
The documentary, which aired at 9pm, saw Theroux visit a California hospital to investigate whether a paedophile can be 'cured'.
Earlier on BBC Two, Top Gear was seen by 2.04m (8.7%) at 8pm.
My Family continued to perform well for BBC One, drawing 4.38m (18.7%) during the 8pm hour. Figures then dropped to 3.87m (16%) during the final episode of The No.1 Ladies' Detective Agency.
Over on ITV1, a new series of Beat The Star started the evening with 5.41m (26.1%) between 7.10pm and 8.20pm.
Heartbeat followed, pulling in 6.02m (24.9%), then 4.46m (19.5%) tuned in for Marco Pierre White's Hell's Kitchen between 9.20pm and 10.20pm.
Channel 4's Come Dine With Me put in 2.45m (10.4%) at 8pm. The audience then rose to 2.66m (11%) during the 9pm screening of The Secret Millionaire.
Five's film fest kicked off with Godzilla, which delivered 1.18m (5.7%) between 6.30pm and 9pm. Rush Hour followed, drawing 1.68m (7.9%) between 9pm and 11pm.
Overall, ITV1 led primetime with an average share of 22.1% to BBC One's 18.2%. Channel 4 was third with 8.4% (+1: 0.8%), followed by BBC Two's 8.8% and Five with 6.8%.
Elsewhere, Lost averaged 778k (3.5%) for Sky1 at 9pm, beating ITV2's Supernatural, which took 671k (3%).
The latest episode of E4's Desperate Housewives was seen by 480k (2.9%) at 10pm.
Ratings data supplied by Attentional