The opening episode, which delved into Davina McCall's family history, was seen by 6.43m (26.6%), making it the most-watched programme during the 9pm hour.
Its nearest rival, the return of BBC Two's Dragons' Den, managed 2.8m (12.5%). The series seven opener, featuring Peter Jones and Deborah Meaden, was down on last series' average of 3.44m (14.4%).
Also at 9pm, Real 999 Calls took 2.76m (12.3%) for ITV1, 1.93m (8.6%) tuned in for the latest visit to the Big Brother house on Channel 4, and Five's Mel Gibson film The Patriot pulled in 1.22m (7.4%) between 9pm and 12.15pm.
ITV1's The Bill led the 8pm hour, drawing 4.84m (24.2%). A new BBC One series, Seaside Rescue, had 4.33m (21.7%), while a revised repeat of Channel 4's Embarrassing Bodies grabbed 1.83m (9.2%).
Build A New Life In The Country interested 1.02m (5.1%) for Five, and 1.1m (5.5%) tuned in for new BBC Two series Home For Life.
Overall, BBC One came top during primetime with an average share of 23.1% to ITV1's 21.1%. Channel 4 was third with 7.1% (+1: 1.1%), followed by BBC Two with 6.6% and Five's 4.8%.
Elsewhere, the second episode of Jo Brand's BBC Four comedy drama Getting On was seen by 347k (2.4%) at 10.30pm, a drop of 381k from last week's impressive start, which aired at 9pm.
The penultimate episode of Gossip Girl was seen by 148k (0.8%) on ITV2, with a further 87k (0.4%) tuning in on timeshift.
BARB ratings data supplied by Attentional