Steven Moffat story 'Day of the Moon', an explosive episode guest-starring Alex Kingston and Arthur Darvill, grabbed 5.39m (30.5%) from 6pm, down 1.1m on last week's series premiere.
The sci-fi drama was neither aided by its early timeslot, nor by the BBC One schedule surrounding it: just 1.39m (10.5%) watched Don't Scare The Hare at 5.30pm, while So You Think You Can Dance had 3.06m (16.7%) from 6.45pm, just pipped by Sing If You Can's 3.14m (17%) for ITV1.
Departures for Stephanie Powell and Gian Luca Loddo from the talent show logged 3.15m (13.9%) at 8.50pm, after which a Casualty instalment titled 'Momentum' took 4.64m (20.5%), beating Piers Morgan's Life Stories on ITV1, which interested 3.51m (15.5%) and 192k on timeshift as Ann Widdecombe sat in the chair.
Britain's Got Talent pulled in 9.08m (40%) at 8pm, enough to topple The National Lottery: Who Dares Wins's 4m (17.6%). Got Talent added 394k on +1, while Britain's Got More Talent with Stephen Mulhern averaged a hefty 1.19m (5.3%) for ITV2 and 178k on +1.
Over on BBC Two, coverage of the snooker World Championship scored 1.94m (7.4%) from 7pm, then Have I Got A Bit More News For You amused 1.83m (8.2%) at 9.45pm.
Elsewhere, Davina McCall's Million Pound Drop entertained 1.93m (8.6%) at 10pm, adding 268k on Channel 4 +1, while CSI: Miami managed 1.68m (9%) for Channel 5 at 10.15pm.
Overall, ITV1 led primetime with 21.6% (+1: 0.9%) to BBC One's 18.6%. BBC Two claimed third place with 8.5%, followed by Channel 4 with 6.2% (+1: 0.8%), and Channel 5 with 5.2%.
BARB ratings data supplied by Attentional