I don’t usually get home in time to watch Watchdog but caught the end of this week’s programme (7.30, BBC1, 2 February) just as it launched into an ‘investigation’ into supermarkets.

Not that it was much of an investigation. In a move as unlikely as Sir Terry Leahy switching allegiance to Liverpool (or Asda), news chihuahuas Nicky Campbell and Julia Bradbury eschewed the opportunity to look at the treatment of suppliers, unethical practices or OTT environmental claims to ask viewers whether they’d changed their shopping habits in the downturn – more specifically whether they were flocking en masse to the discounters.

Now I know this was aimed at consumers, but it was about as insightful as Carol Thatcher on race relations. To whet the viewer’s appetite, Julia trekked to her nearest Lidl (pronounced Leedl, don’t you know) to show us all what one looked like. Guess what? Goods were piled high and sold cheap – and there were brands she’d never heard of (they’re called own label, Julia).

As they listed the discounters, Netto was named first despite having the smallest share and it soon became clear why when Netto boss Charles Kay was wheeled out to inform us that, wait for it, people no longer felt so ashamed about shopping in a discounter that they hid purchases inside an M&S carrier.

The revelations kept coming. Two couples – one middle-class and one working-class – were ‘challenged’ to try out new stores. When Sainsbury's-loving Natasha and Angus gave Aldi a go, he liked the fact it was smaller and easy to navigate, but she turned her nose up at the lack of familiar brands and offers. Meanwhile, Tesco fans Natalie and Dave loved Waitrose though he initially thought it was “to do with people trying to lose weight” – bless – and both found it a tad pricey.

Three out of four said they’d shop at their new stores again. But will they? The problem with a survey like this is that it can only establish what people say they do, not what they actually do. Look at switching data and the winners and losers in the supermarket vs discounter wars are not as obvious as the Watchdog crew may think.