A new episode of the topical panel show, which featured Sherlock's Benedict Cumberbatch as guest host, averaged 5.24m (21.6%) for BBC One between 9pm and 9.30pm.
The programme was followed on the channel by a new series of the Martin Clunes-starring comedy Reggie Perrin, which amused 3.21m (14.2%).
Earlier on BBC One, The One Show was watched by 4.4m (21.2%) from 7pm, before Watchdog grabbed 4.1m (17.2%) in the 8pm hour.
On ITV1, Tonight: Bullies Online scooped 2.45m (10.8%) between 7.30pm and 8pm, while 115k (0.5%) tuned in on ITV1 HD. Law & Order: UK pulled in 4.24m (18.2%) on the channel from 9pm and 162k (0.7%) in HD.
Channel 4's River Cottage Every Day brought in 1.68m (7%) from 8pm and 304k (1.3%) on Channel 4 +1. Giant Squid: Inside Nature's Giants Special attracted 1.44 (6.4%) to the channel in the 9pm and 241k (1.5%) on timeshift.
Series two of True Blood continued to 620k (4.6%) on Channel 4 from 10.30pm, while 104k (1.5%) tuned in an hour later.
Over at BBC Two, Games Today grabbed 1.17m (5.4%) in the 7pm hour, before Nigella Kitchen cooked up 2.19m (9.4%).
Autumnwatch 2010 appealed to 2.16m (8.9%) between 8.30pm and 9pm, before spinoff show Autumnwatch Unsprung took 2.03m (8.9%). Mock The Week then had 1.9m (9.8%) from 10pm.
Five's World's Most Extreme Airports mustered 1.99m (8.5%) between 7.30pm and 9pm, before a screening of Tears Of The Sun took 1.08m (5.6%) from 9pm.
BBC One narrowly won primetime with 21.1% over ITV1's 20.8% (HD: 0.8%). BBC Two came in third with 7.8%, followed by Five with 6.1% and Channel 4 with 5.7% (+1: 0.9%).
Elsewhere, the biggest multichannel audience of the evening went to An Idiot Abroad, which averaged 1.03m (4.4%) for Sky1 in the 9pm hour.
On ITV2, What Katie Did Next appealed to 962k (4.1%) from 9pm and 187k (1.1%) on timeshift. It was followed by Celebrity Juice: McFly Special, which amused 962k (5.2%) and 142k (1.4%) an hour later.
BARB ratings data supplied by Attentional