'The Human Spider' was watched by a 10.8% share of the audience at 9pm, rising to 2.8m and 12.2% including Channel 4+1. The programme was backed with on-air trails.
The 'Cutting Edge' series has put in a strong performance this year, averaging 2.5m viewers and an 11.4% share in 2008, compared to 1.5m and 6.9% last year.
Recent documentaries to score highly with viewers have included programmes on call centres and so called "phone rage", a music prodigy suffering from cystic fibrosis and a behind-the-scenes film on the family of Shannon Matthews in the days leading up to her rescue.
BBC One triumphed in the 9pm slot with a one-hour film narrated by Jamie Theakston on London's Economic Crime Unit. 'Identity Fraud: Outnumbered' drew 3.9m viewers and a 17% share.
Five's popular US import 'House', which stars British actor Hugh Laurie, brought 2.1m viewers and a 9% share at 9pm.
ITV1's 'Holiday Homes from Hell' gave viewers a look at what happens when the purchase of a dream holiday home leads to disaster, with 3.5m viewers and a 15.1% share at 9pm.