Were Bonnie Tyler to sing Holding Out for a Hero now - obviously a faintly ludicrous proposition, as she clearly is singing Holding Out for a Hero now, in a working men's club somewhere on Barry Island, non-stop, like in They Shoot Horses, Don't They?, just in order to pay her gigantic hairspray and tracheotomy bills; but you know what I mean - the lyrics would not run “He's got to be strong/ And he's got to be fast/ And he's got to be fresh from the fight.”

For in 21st-century Britain, we do not need some sweaty-cracked brawler “racing on thunder and rising with the heat”. For what are we, in essence? A group of credit-card waving children. A bunch of fat spendaholics trying to get the best, because we're “worth it”. A nation who would cede to Hitler on the first day of the Second World War, half an hour after the Nazi naval blockade terminated the Starbucks supply of hazelnut-flavoured syrup.

And so who would a hero be to us, in our current state? It would be someone who really knew how to buy stuff. Someone who could really work those shelves. Some manner of consumer maven. Someone like Esther Rantzen, but without the turnip that looks like a bifurcated penis.

And so, cometh the hour, cometh the razzy BBC prof. We already know Professor Lesley Regan, of course. It was her Horizon on anti-ageing face creams which, last year, prompted a run on Boots Protect and Perfect cream. Even now - 13 months later - Boots' advertising campaign for the product revolves around Professor Regan's endorsement, and sales remain high. If cranberries and omelette pans can benefit from the “Delia effect” whenever Smith-o gives them the nod, then, clearly, pretty much everything else in the supermarket could prosper from a name-check from Prof Lesley Regan. (These are the new “Regan-omics”.) We could even refer to any nascent sales-boom phenomenon as “Les-ing it up”.

However, despite the BBC's high hopes for the prof's putative role as Supermarket Jesus, her second Horizon: Professor Regan's Supermarket Secrets - falls a little flat. Tackling seven products - 30-degree washing powders, anti-bacterial kitchen sprays, “superfoods”, organic food, pro-biotics and cholesterol-lowering marge - the prof wades into action in her kitten-heels, resembling a younger Joan Bakewell who is having to ask a lot of sceptical questions about Unilever.

“What is the research? Are there side-effects? You're treating this as if this was something that we all accept to be true,” she says, over a series of “looking knowledgably at graphs and stats” shots.

And despite the prof's essentially negligible qualifications to be the voice of scientific certainty - she's an obstetrician by day, “so she understands what medicine does and if it's proven to work,” the voiceover supplies, helpfully; kind of ignoring that there isn't an obvious link between doing a cervical sweep and knowing if Persil is good or not - the programme ostensibly appears to deliver results. Thirty-degree washing powders do work, while organic food is a waste of money. And anti-bacterial sprays are confirmed as one of the most powerful forces on Earth - able to dispatch e coli, hepatitis and, practically, death, with one squirt.

But the problem with Professor Regan's Supermarket Secrets is the problem with her first Horizon. The scope of the tests is narrow, and very brand-specific. While her first programme concludes that, yes, Boots Protect and Perfect does work, what isn't mentioned is that the research Regan quoted concluded that any face cream with the same active ingredients would give the same result.

Likewise, here, the efficacy of low-temperature washing powders simply comes down to pitching Ariel against “a supermarket brand” - bafflingly ignoring all other brands. Much of the superfood debate, meanwhile, focuses solely on a single flavour of Innocent smoothies - somehow devolving the entire debate on the nature of antioxidants down to one man with a blender in West London.

For a nation crying out for some manner of consumer hero, Regan's skills in supermarket pugilism seem ineffectively narrow - a bit like if, when Bonnie Tyler's hero had turned up, he was neither fast, strong nor fresh from the fight, but was a regional champion in bobsledding and darts.

Still, prepare to see Ariel become like eBay gold-dust by Friday.

Horizon: Professor Regan's Supermarket Secrets, Tues,

BBC Two, 9pm

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