May was not a good month for supermarket leviathan Tesco.
The BBC's Whistleblower programme sent undercover reporters to work in branches of Tesco (and Asda) and found workers changing the use-by date on food.
Tesco's ratings on BrandIndex reacted as you'd expect - its buzz fell by 22, its quality by six.
Despite its huge popularity with shoppers and dominance of the market, Tesco has a brand image problem: it seems to have become the media's personification of a big, impersonal corporation crushing local shops underfoot.
Its latest ad campaign is clearly intended to address that by pushing Tesco's premium localchoice milk, which pays increased revenues to small local dairy farmers.
The new ads feature Doc Martin star Martin Clunes and Fay Ripley from Cold Feet as a couple camping in the countryside.
Determined to show he isn't a clueless townie, Clunes goes off to find a cow to get fresh local milk for their cereal - except, reluctant to do any of the actual hands-on cow milking, he instead buys it from Tesco's localchoice range.
He would have got away with it too, except that the milk is suspiciously chilled for something that is supposed to have come fresh from a cow.
With an ad aimed at showing Tesco is both convenient and busy supporting local farmers, has it improved the brand image?
Since the campaign was launched on 1 June, Tesco's buzz has increased from -7 to +2, quality is up from +24 to +32 and value is up from +32 to +36.
However, while on the surface it looks as though the ad has been a stunning success, part of the rise is probably just Tesco recovering from the bad publicity hangover of the BBC's Whistleblower programme. Despite the boost, its buzz and value ratings are still below those that Tesco enjoyed before the expose.
It seems it will take more than the good Doc to mend the wounds.
YouGov's BrandIndex is a daily measure of public perception of more than 1,100 consumer brands across 32 sectors, measured on a seven-point profile, with data delivered on the next day.
YouGov interviews 2,000 people each weekday, more than half a million interviews per year.
This means you can spot trends as soon as they happen, not when it's too late. Respondents are drawn from an online panel of more than 130,000.
The score is the net rating: people are asked to identify the brands to which they have a positive response, and then those to which they have a negative response, to whatever is the prompt measure.
The net score is the positive minus the negative.
The seven measures that make the complete profile are below.
Each is taken independently - in any one survey, any individual respondent is asked about only one measure for the sector, not all seven. Therefore, none of the readings influence each other within the survey.
2. General impression
7. Corporate reputation
In addition, we supply an index score.
by Sundip Chahal