Once you pop, Pringles used to say, you can't stop.

That was before the dawn of the obese époque, when we became a bloated nation of beached whales gurgling cholesterol through our lipid-encrusted blowholes. Now if you don't stop after the second crunch, the health police will march you out back and shoot you.

Happily, another ancient law of grocery is back on TV: stick a Fruit Pastille in your gob and you have to chew.

So goes the theme for the Rowntree's stalwart's first ad since 2007. Never mind the medieval trappings of the Chew Challenge troupe, whose chartist badinage hints at an unfulfilled longing for the silliness of the popular Randoms campaign. And lust not for the suitably toothy maiden whose hand, honour and hectares of gums are offered to any noble chew-eschewer.

The theme is immutable, immortal, as irresistible as a gelatinous blob imbued with E numbers. Just bite, baby.

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