'Broken Heart Syndrome' averaged 5.11m (22.3%) from 8.50pm, representing a slight drop on last week's episode.
Other big shows tumbled further as ITV's Splash! semi-final took 4.84m (21.3%) in its usual 7pm slot, adding 267,000 on +1.
Take Me Out and Jonathan Ross followed with respective audiences of 3.96m (17.4%) and 2.49m (12.8%), as well as 200k and 241k on +1.
Over on BBC One, Richard Hammond's Secret Service (1.96m/10%) from 6pm and Britain's Brightest (3.81m/17.3%) at 6.45pm sank to new lows, after which 8pm's In It To Win It dipped to 4.69m (20.3%).
Indeed, only Mrs Brown's Boys (4.62m/22.2%) and ITV's You've Been Framed managed to rise week-on-week, the latter entertaining 4.67m (23.4%) and 169k on +1.
Classic sitcom Dad's Army was BBC Two's most-watched broadcast with 2m (8.6%) at 8pm.
Mrs Doubtfire proved a steady choice by Channel 4 schedulers, putting in 1.43m (6.4%) from 6.45pm (+1: 250k), while Channel 5 suffered a Celebrity Big Brother hangover as its film Impact could only muster 828k (3.7%) in comparison.
BBC Three managed to usurp the Richard Desmond network thanks to its screening of Pirates of the Caribbean: The Curse of the Black Pearl, which attracted 1.18m (5.5%) from 8.30pm.
Overall, BBC One reigned victorious in primetime with 19.7%, ahead of ITV's 17.7% (+1: 1%). BBC Two claimed third place with 6.7%, beating Channel 4's 5.5% (+1: 1%), BBC Three's 4.1%, and Channel 5's 3.7% (+1: 0.4%).
BARB ratings data supplied by Attentional Get the Inside Soap magazine on your iPhone or iPad