The episode, titled 'Blood On The Saddle', averaged 5.53m (24.7%) for ITV1 between 8pm and 10pm. An additional 154k (0.7%) tuned in on ITV1 HD.
The programme helped ITV beat the BBC in primetime, after Waterloo Road and Crimewatch pulled in respective audiences of 4.11m (18.6%) and 3.5m (15.4%) on BBC One from 8pm. A further 137k (0.6%) watched Waterloo Road on BBC HD.
The One Show grabbed 3.51m (19%) on BBC One from 7pm, before Bang Goes The Theory returned to 2.98m (15.7%).
On ITV1, tribute programme The Unforgettable Mollie Sugden appealed to an impressive 4.81m (25.4%) between 7.30pm and 8pm.
Over at Channel 4, How To Look Good Naked brought in 1.42m (6.5%) from 8pm and 204k (0.9%) on timeshift, before Ultimate Big Brother took 2.6m (11.4%) in the 9pm hour and 340k (1.9%) on Channel 4 +1.
Derren Brown's Hero at 30,000 Feet attracted 2.43m (14.7%) from 11pm and 197k (2.2%) on Channel 4 +1, before live coverage of Ultimate Big Brother's double eviction grabbed 1.87m (20.2%) from 11.15pm and 75k (1.8%) on timeshift.
New series Queens Of Heartache brought in 1.15m (6.1%) on BBC Two in the 7pm hour, before Coast averaged 2.05m (9.3%). The Big School Lottery took 1.22m (5.4%) from 9pm, and it was followed by Grumpy Old Holidays, which secured 1.64m (8.4%).
On Five, Michaela's Zoo Babies attracted 567k (3%) from 7.30pm, before Emergency Bikers took 1.17m (5.3%) in the 8pm hour.
NCIS secured 1.27m (5.6%) on Five in the 9pm hour, and it was followed by Law & Order: Criminal Intent, which mustered 1.05m (5.8%) from 10pm.
Overall, ITV1 won primetime with 22.6% (HD: 0.5%) against BBC One's 17.6%. Channel 4 came in third with 8.7% (+1: 1%), followed by BBC Two with 7% and Five with 4.7%.
Elsewhere, a new series of acclaimed drama Mad Men debuted to 336k (1.8%) on BBC Four from 10pm.
However, the biggest multichannel audience of the night went to a screening of Under Siege 2: Dark Territory, which took 844k (3.9%) on BBC Three between 9pm and 10.30pm.
BARB ratings data supplied by Attentional