In 1959, Mars chocolate bars were first sold on the basis that they were a powerhouse of nutrition, a quick and convenient of helping UK consumers "Work, Rest and Play…" when eaten once a day. The slogan caught on, propelling the quasi-monolithic nougat, chocolate and caramel bar to the upper echelons of the British chocolate market.

More than 40 years on, however, Mars' producer, Masterfoods, has decided the game is up. As society changes, the slogan's compartments are no longer valid to a modern lifestyle. Not forgetting the fact that chocolate is a staple for many, and no longer a rationed commodity. 

From this week, the bar will be smaller, lighter, packaged with a new modern typeface and sold under the promise of "Pleasure You Can't Measure". The push will be to attract to a more female, youthful audience, and thus drive sales growth in what is essentially a mature market.

Sophia Nadur, brand manager for Mars UK, explained to the Guardian that in the 1950s, "Brits didn't trust the idea of feckless pleasure".

Now, however, Mars could appeal to a more exciting chocolate eater, and a smaller lighter bar could increase consumption per capita: "While people loved the anticipation of biting into the chocolate, they often found that the bar lay rather heavily on their stomach at the end of eating it.

"Which means they wouldn't eat another, sometimes for the rest of the day."

The relaunch, with its advertising support, is costing Masterfoods more than £10m (US$14.23). By the end of this month, British consumers will see short, quirky adverts that highlight the little pleasures in life.

Tim Mellors, chairman and creative director at Grey Worldwide marketing group, told the paper: "The consumer these days is visually smart and very hip. You don't have to spell out your strategy or repeat your message hundreds of times." 

"Mars used to hit people over the head a little bit too much."