A little bit of evidence of the popularity of some of these programmes...
BARB viewing figures for week ending 23/09/2007 - BBC2
http://www.barb.co.uk/
Top programme was Nigella Express on the Monday - over 3 million
Third was Tribe on the Tue - nearly 3 million
Wild Food was 11th, shown on Sunday, just over 2million
The programme actually started the week before but didn't make the top 30 (?!)
which is a surprise but it didn't seem to be advertised much so maybe not.
For comparison, Coronation Street gets over 11 million and it's on a different channel.
and for UKTV Documentary (the actual viewing figures are lower overall)
UKTV Documentary TOP TEN PROGRAMMES
Rank Programme Time Audience
1 Ray Mears's Wild Food.......13 July 07........2100........67,000
2 The Blue Planet 27 May 07 1500 56,000
3 Ray Mears's Extreme Survival 11 July 07 2200 56,000
4 Amazon - Truth and Myth 06 July 07 2000 52,000
5 The Natural World 31 May 07 1400 51,000
6 The Secret Of El Dorado 16 June 07 2100 48,000
7 Wild Africa 24 June 07 2000 47,000
8 Planet Earth 29 July 07 2100 44,000
9 Tribe 20 June 07 2000 43,000
10 Wild Indonesia 27 June 07 1700 42,000
(I put dots in the first line for clarity. Name, date, time, number of viewers).
Source: BARB/TNS, May 2007 - July 2007. The top 10 shows are the best performing episodes only of each programme, based on Individuals.
http://www.idigitalsales.co.uk/channelperformance/channelperformance.cfm?sectionid=17
Not too shabby