Their last ever con was seen by 5.34m (22.9%), overtaking 9pm drama rival Law & Order: UK, which slipped to 4.32m (18.5%) on ITV1 (+1: 294k/1.6%).
Elsewhere in the hour, George Lamb gameshow The Bank Job could only muster 913k (3.9%) for Channel 4 (+1: 171k/0.9%), outperformed by Channel 5's The Mentalist (1.13m/4.9%), and BBC Two's Baka: A Cry from the Rainforest (1.13m/5.1%).
Room 101 held 3.4m (14%) for BBC One at 8.30pm, while New Girl climbed to 854k (3.5%) and 148k (0.6%) on Channel 4 +1.
At 8pm, Safari Vet School had 2.45m (10.4%), Mastermind grabbed 2.08m (8.8%) for BBC Two, and 1.04m (5.3%) watched World's Toughest Trucker on Channel 5.
After last week's 4.1m audience, The Graham Norton Show fell back to 3.48m (23.3%) for BBC One at 10.35pm.
Overall, ITV1 edged primetime with 22.5% (+1: 0.8%), ahead of BBC One's 21.6%. BBC Two claimed third place with 5.9%, ahead of Channel 5's 4.2%.
Meanwhile, Sky1's Stella stayed strong with 660k (2.3%).
BARB ratings data supplied by Attentional