The Martin Compston drama held a solid 3.14m (13%) in the 9pm hour, helping BBC Two overtake BBC One in the 9pm hour.
Who Wants to be a Millionaire? gave ITV1 a rare and narrow victory in the slot, attracting 3.23m (13.4%) and a further 205k (1.1%) on +1.
BBC One's Turn Back Time: The Family finished third in the hour with 3.1m (12.8%), ahead of Gordon Behind Bars which had 2.09m (8.7%) for Channel 4 and 275k (1.4%) on timeshift.
Meanwhile, CSI logged 2.09m (8.7%) for Channel 5, appealing to 151k (0.8%) an hour later. Big Brother drew 1.33m (6.9%) an hour later at 10pm.
Hugh Bonneville's Olympics sitcom Twenty Twelve returned to BBC Two with 1.2m (5.6%) immediately after Line of Duty, while 2.24m (10.2%) watched Volcano Live at 8pm.
Elsewhere in Channel 4's schedule, Beauty and the Beast: The Ugly Face of Prejudice interested 1.2m (5.5%) at 8pm (+1: 184k/0.8%), and Secrets of the Shoplifters mustered 1.68m (8.9%) from 10pm (+1: 317k/3.2%).
Love Your Garden delivered 3.06m (14%) to ITV1 at the 8pm junction, adding 164k (0.7%) on +1.
Overall, BBC One topped primetime with 19.4%, beating ITV1's 14.3% (+1: 0.6%). BBC Two earned third place with 8.3%, ahead of Channel 4's 6.7% (+1: 0.9%), and Channel 5's 5% (+1: 0.3%).
Geordie Shore: Chaos in Cancun continued with a loyal 467k (2.5%) on MTV at 10pm.
BARB ratings data supplied by Attentional