In January last year, Mars announced plans to reformulate the Mars bar.

It was a historic move: while other chocolate confectioners were signing up to Fairtrade this and Rainforest that, the UK’s favourite chocolate bar invested £9m over five years to come up with a bar containing 15% less saturated fat.

Yet what happened next was surely not in the plan: as we reveal this week, in our special supplement on Britain’s 100 Biggest Brands, sales in the last year have slumped by £17m, or 14%.

So what’s gone wrong? Its problems appear to involve both bad luck and poor judgement. Its misfortune was to back the misfiring England football team. It was difficult to unwrap one of those red and white wrappers without a sense of shame at the ineptitude of England’s performances in the World Cup (while a Scottish T-shirt wittily proclaimed My Arse… Believes).

But a Mars World Cup ad featuring John ‘Fatty’ Barnes in a rehash of the 1990s New Order single World in Motion was an own goal right up there with the FSA’s use of Dawn French to promote its traffic light ads, sending out all the wrong signals, in terms of both health and modernity.

Of course Mars has been a trendsetter in the past with early extensions into milk and ice cream, and its development of sharing bags. But it has run out of ideas to keep the brand live and current, in terms of positioning, packaging and product, as rivals have stolen the caramel trend from under its nose.

With other Mars brands such as Planets also in decline, it’s massively stepped up promotions this month (p5). But why, having done “the right thing”, is the messaging around reformulation at the level of a whisper?

No-one can suggest a Mars bar is as nutritious as those other quotidiens, the apple and the egg. But did Walkers keep quiet over its superb reformulation? Did Rowntree? Did McCain? Did supermarkets?

No. Mars, like England, had a great chance, and blew it!