Episode three of the six-part romantic drama pulled in 6.23m in the 9pm hour, a 26.5% share.
Even higher than November's premiere audience, the series grew 700k week-on-week.
With EastEnders and Holby City performing solidly earlier on, BBC One towered over ITV, which could only average 3.03m (12.8%) for its Champions League football coverage between 7.30pm and 10pm.
MasterChef: The Professionals anchored BBC Two's schedule with an impressive 3.2m (13.2%) at 8pm, after which 1.23m (5.2%) watched Dara O'Briain's Science Club, and The Sarah Millican Television Programme returned with 1.19m (6.3%) in the 10pm slot.
Elsewhere, 5 secured 1.08m (4.5%) for 8pm's Murder Files: The Haircut Killers and 1.06m (4.5%) for 9pm's Body of Proof. Channel 5 +1 added 142k for Body of Proof.
Overall, BBC One thrashed ITV1 in primetime with 24.2% to 14.1% (+1: 0.4%). BBC Two eased into third place with 7.7%, beating Channel 4's 5.6% (+1: 1%) and Channel 5's 3.8% (+1: 0.3%).
BARB ratings data supplied by Attentional