The episode, which featured Peter Jones and Duncan Bannatyne backing a healthy ice cream entrepreneur, was watched by 3m (12.7%) on BBC Two in the 9pm hour.
It was a good night for BBC One as Waterloo Road grabbed 4.2m (19.5%) in the 8pm hour and the third part of drama The Silence took 4.05m (17.2%) from 9pm.
In comparison, Midsomer Murders averaged just 3.81m (16.9%) for ITV1 between 8pm and 10pm.
On ITV2, the first episode of Katie & Alex: For Better For Worse appealed to 973k (4.1%) in the 9pm hour, which was the largest multichannel audience of the night. The programme also pulled in 203k (1.1%) on timeshift.
The latest episode of Big Brother took 2.31m (13%) for Channel 4 between 10pm and 11.10pm. A further 189k (2.1%) watched the show on Channel 4 +1.
How To Look Good Naked pulled in 1.92m (8.9%) from 8pm and 206k (0.9%) on timeshift. It was followed by Living With Brucie, which took 2.35m (10%) in the 10pm hour and 359k (1.9%) on Channel 4 +1.
How To Beat Tough Times: Money Watch brought in 1.64m (7.6%) for BBC Two in the 8pm hour. Later on the channel, sitcom Rev secured 790k (3.8%) between 10pm and 10.30pm.
Battle Of Britain: The Lost Evidence appealed to 1.36m (6.3%) for Five in the 8pm hour, and NCIS secured 1.01m (6.3%) between 9pm and 10pm.
Crime drama series K-Ville averaged 384k (3.9%) for Five in the 11pm hour, down 243k week-on-week.
Overall, ITV1 narrowly won primetime with 19.9% against BBC One's 18.1%. Channel 4 came in third with 8.8% (+1: 0.9%), followed by BBC Two with 7.7% and Five with 4.6%.
BARB ratings data supplied by Attentional