The third episode of this year's series averaged 11.76m (51.9%) between 7.35pm and 8.35pm, up from last week's 9.75m (47.1%).
The figure also represents an increase of a huge 3.6m on the equivalent episode from last year's series, seen by 8.16m (43.5%) on August 30, 2008.
Last night the audience peaked with 12.87m (55.4%) at 8.10pm.
ITV2 spinoff show The Xtra Factor put in 1.55m (7.5%) at 8.35pm, with an additional 122k (0.6%) watching on ITV2+1. Repeats of both programmes delivered 315k (4.4%) and 176k (4.5%) for ITV2 from 11.40pm.
Earlier on ITV1, live coverage of England's friendly with Slovenia averaged 5.36m (33.7%) between 4.45pm and 7.35pm.
After The X Factor, Phillip Schofield gameshow The Cube appealed to 4.99m (22.4%), then a repeat of It'll Be Alright On The Night had 3.81m (19%).
On BBC One, The National Lottery: Big 7 - this year's Lottery Awards, fronted by Nick Knowles and Myleene Klass - drew just 2.35m (10.7%) from 7.15pm. At 8.45pm, a screening of the first Pirates of the Caribbean movie put in 4.71m (22.9%).
BBC Two had success with a Beatles-themed evening, beginning at 7.45pm with 1.59m (6.9%) for a Timewatch special on Beatlemania. 50 minutes later, The Beatles: On Record was seen by 2.49m (11.2%), then The Beatles: The First US Visit grabbed 1.52m (7.7%). A screening of 1965's Help! rounded out the evening with 880k (7.9%) at 10.45pm.
Channel 4's ER double-bill - including the penultimate episode ever - picked up audiences of 413k (2%) and 388k (1.7%) from 7.05pm. At 9pm, a screening of 9/11-themed movie World Trade Centre was of interest to 1.02m (5.3%).
Five's night of US reruns started at 6.45pm with The Guardian, which picked up 680k (3.5%). The audience grew to 1.07m (4.7%) for NCIS at 7.40pm, then built further still to 1.51m (6.8%) for CSI: Miami at 8.35pm. CSI logged 1.43m (7%), then Law & Order: SVU finished the night with 981k (6.7%) at 10.35pm.
ITV1 was comfortably in the lead in primetime overall, registering an average audience share of 30.7% to BBC One's 18.2%. BBC Two was third with 8.6%, followed by Five with 5.7% and Channel 4 with 3.4% (+1: 0.8%).
BARB ratings data supplied by Attentional