The two hour episode, in which Dannii Minogue sparked outrage for making a suggestive comment about Danyl Johnson's sexuality, averaged 11.31m (43.8%) for ITV1 between 8pm and 10pm.
It beat BBC One's rival reality series Strictly Come Dancing, which managed 8.03m (32.3%) between 7pm and 9.15pm. Earlier, at 6.15pm, the fourth instalment of Merlin, which saw Gwen kidnapped by Hengist, drew 5.08m (27.1%).
After Strictly, The National Lottery Draw grabbed 4.86m (19%), then a new episode of Casualty managed 4.61m (19.3%) between 9.25pm and 10.15pm.
Completely ITV1's primetime lineup was Piers Morgan's Life Stories - this week featuring Cilla Black - which interested 4.21m (22.1%) during the 10pm hour.
Over on BBC Two, 870k (3.3%) tuned in for Ghandi at 8.20pm, then Have I Got A Bit More News For You put in 1.6m (6.4%) an hour later.
Channel 4's film double kicked off with Oliver Twist, which drew 730k (2.9%) between 7.30pm and 10pm. Blade II followed, averaging 1.28m (8.2%) between 10pm and 12.10am.
Five's double-bill of CSI: New York had 818k (3.1%) then 731k (2.9%) at 8pm and 9pm respectively, then 1.04m (2.9%) watched CSI during the 10pm hour.
Overall, ITV1 came top during primetime with an average share of 35.3% to BBC One's 27.4%. BBC Two was third with 4.2%, followed by Channel 4 with 3.7% (+1: 0.2%) and Five's 3.8%.
Elsewhere, the Holly Willoughby-fronted Xtra Factor put in a respectable 1.35m (7.4%) for ITV2 during the 10pm hour.
BARB ratings data supplied by Attentional