Carrot-munchers 1; global confectionery giant 0. For millions of people around the world, Sunday's climbdown by the makers of Mars Bars was a particularly sweet success.

I use the term "carrot-munchers" affectionately, being one myself. Indeed, in the six years since I joined the ranks of the veggie brigade, I've lost count of the number of times it's been sneeringly suggested that carrots are all I eat. But I'm in extraordinarily glamorous and ethically conscious company: Stella McCartney, Joanna Lumley, Gwyneth Paltrow and Chris Martin to name but four. And, when it came to the crunch, this was a resounding veggie victory.

The issue was simple: the decision by Masterfoods to change ingredient suppliers, meaning trace amounts of rennet - a natural enzyme produced from the stomachs of calves - would be found in some of its products, including Mars bars, Galaxy and Maltesers. This put the products strictly off-limits for vegetarians: but now, after the company's public climbdown, we will soon be able to guzzle them to our hearts' content once more.

You don't have to be a vegetarian to find something extremely gratifying in this. For at the heart of the issue is good old-fashioned people power. It just so happens that the people in question have tended, up until now, to take a bit of a kicking for their gastronomic leanings.

Masterfoods is an extremely powerful player, with a share of the UK confectionery market estimated at 30%. The fact this giant has made a public apology and performed a U-turn signals just how important the veggie pound has now become.

There were no pickets, no mass demonstrations - just an estimated 6000 or so phone calls and e-mails to the company. Forty MPs were among those who signed a protest petition, according to the Vegetarian Society.

Masterfoods' response was rapid and contrite. "It became very clear, very quickly, that we had made a mistake, for which I am sorry," explained Fiona Dawson, managing director of the Mars snack food business in Britain. "There are three million vegetarians in the UK and not only did we disappoint them, but we upset lots of other consumers.

"We have listened to their views and have decided to reverse our decision." She added: "I personally commit to make sure that the products we changed will be suitable for vegetarians again in the near future."

At the time of the original announcement, the Vegetarian Society described the plan to change the existing recipe as "incomprehensible" and "a backward step", particularly given that consumers are increasingly "concerned about the provenance of their food".

Now, after a week of quiet but determined protest, here we have it: proof that even the biggest companies can capitulate if enough people are prepared speak up.

Yet who was it who led the charge? Yes: we poor, oft-maligned vegetarians. Think about that next time you make a disparaging comment about carrots. Who says you need to eat meat to grow up strong?