The original three-part tale, about the strange events relating to a mysterious door knocker, started with an impressive 517k (3.3%) for the channel at 10.30pm last Monday, December 22.
It was the fifth most-watched multichannel programme and the most popular original multichannel programme of the day. The top audience was 764k (4.1%) for BBC Three's EastEnders repeat, followed by 720k (6.3%) for ITV2's screening of Love Actually from 10pm.
Among the terrestrial channels, a Christmas edition of QI was particularly popular in its 9pm slot on BBC One. The special episode, guest starring Clive Anderson and Rob Brydon, drew an impressive 5.11m (21.5%). It was followed by Gavin & Stacey, which took 3.86m (16.7%).
On ITV1, The Bill had a reasonable 4.94m (21.1%) in a later 9pm timeslot.
Two episodes of Coronation Street brought in 9.17m (40.1%) and 9.12m (37.7%) at 7.30pm and 8.30pm respectively, while EastEnders notched up 9.12m (38.2%) for BBC One at 8pm. Emmerdale was on 7.07m (33.9%) at 7pm.
ITV1 had a 24.6% share in primetime (last week: 27.1%) to BBC One's 20.3% (22.7%) average.
On Channel 4, the final episode of The Ascent Of Money drew 0.83m (3.4%), placing the channel last for the 8pm hour. The audience doubled at 9pm for the final Catastrophe, with 1.65m (7%), then a screening of Father Ted's Christmas episode kept 1.59m (9%).
Earlier, a double-bill of Hollyoaks put in a decent 1.51m (7.8%) in the 6pm hour, then another double-bill had 486k (2.5%) for E4 (+1: 80k, 0.4%). In primetime Channel 4 had an average share of 5.7%, up on last week's 5%.
The series finale of The Gadget Show pulled in 1.06m (4.4%) to Five in the 8pm hour, then a screening of police comedy Hollywood Homicide averaged 774k (3.9%) until 11.20pm. The channel's primetime share was 3.4%, from 3.7% last week.
Ratings data supplied by Attentional