Davina McCall and Nicky Campbell's reunion show grabbed 4.22m (19.7%) in the 9pm hour, adding 229k on ITV1 +1.
With Crimewatch only able to muster 3.41m (15.9%) for BBC One, Long Lost Family has now won its slot on all seven Thursdays it aired, never once dipping below 4m.
Meanwhile, new Griff Rhys Jones factual vehicle Britain's Lost Routes drew 2.74m (12.6%) for BBC One in the 8pm hour, predictably losing out to ITV's soap zone.
Springwatch interested 2.04m (9.3%) on BBC Two at 8pm, then 1.45m (6.8%) stayed around for Springwatch Unsprung, and The Meat Market: Inside Smithfield had 1.43m (7.1%) from 9.30pm.
Married to the Moonies made its Channel 4 debut with 1.3m (6.1%) at 9pm (+1: 288k), prior to which Phil Spencer: Secret Agent logged 1.18m (5.4%) at 8pm (+1: 152k), and 24 Hours in A&E managed 1.06m (6.2%) at 10pm (+1: 252k).
World's Scariest Animal Attacks (780k/3.6%) and Cowboy Builders (719k/3.4%) were screened on Channel 5 to fairly modest audiences.
Overall, ITV1 led primetime with 21.9% (+1: 0.8%), beating BBC One's 18.4%. BBC Two claimed third place with 7.1%, ahead of Channel 4's 5.3% (+1: 1%), and Channel 5's 3.5% (+1: 0.3%).
The Big Bang Theory continued to dominate the multichannels with 1.02m (4.9%) at 8pm and 383k (1.8%) on E4 +1, while Russell Howard's Good News entertained 793k (3.7%) at 9pm, and was the most-watched programme on TV at 1am with 415k (13.1%) for a repeat of the clip show.
BARB ratings data supplied by Attentional