'The Artful Codgers' documentary attracted an 11.6% share of the audience from 9pm-10pm.
The documentary makers took a behind-the-scenes look at the Greenhalghes, who were convicted last year of making at least £850,000 from selling forged works of art.
The programme's screening on Channel 4+1 attracted 600,000 viewers giving it a 1.7% share.
Earlier in the evening, cookery-based reality TV series 'Come Dine with Me' boosted its audience by 100,000 viewers on last week, with 2.2m viewers and a 12.4% share at 8pm-9pm. Channel 4+1 figures gave the show 400,000 viewers and a 0.9% share.
ITV1's new crime drama 'Midnight Man', starring James Nesbitt in the 9pm-10pm slot, lost 300,000 viewers from last week's opening episode; 3.5m and a 16.1% share tuned in for the second instalment of the three-part series.
BBC One's comedy drama 'The Invisibles' drew 3.3m viewers and a 15.1% share in the same slot, up from 3.2m last week.
Five's US medical drama 'House' netted 1.5m viewers and a 7% share at 9pm-10pm, below the 1.8m it had last week.
BBC Two's US science-fiction series 'Heroes' shed 100,000 viewers on last week's episode, with 2.6m and an 11.7% share watching at 9pm-10pm.