KIT Kat has been a favourite of the British public since its inception in 1935.

The distinctive red and white logo, and catchline "Have a Break, Have a Kit Kat", have infiltrated the British consciousness to such an extent that it has been among the top-selling brands for Nestle Rowntree for years in a UK chocolate market worth a sweet £4bn a year.

But two years ago, Nestle Rowntree started to lose its way with its favourite brand by experimenting with expensive flavours, limited editions, and failing to advertise as heavily as it had in the past.

In November, Chris White resigned from his post as UK managing director of Nestle Rowntree, believed to be as a result of core brands, such as Kit Kat, losing their market share.

When he joined in December 2003, he set about radically altering the Kit Kat brand - a brand described by one expert as "a design icon, just like the Coke bottle, just like the Ferrari".

He committed what was seen as an act of brand vandalism when he axed the long-standing "Have a Break" logo.

Under his leadership, the company also introduced a myriad of Kit Kat flavours - from Strawberries and Cream to Lemon and Yoghurt, diluting and confusing more than 60 years of brand heritage.

That mistake could end up costing jobs at Nestle's York factory.

Yesterday, Dr Joan Harvey, consumer psychologist at Newcastle University, believes Nestle committed a "monumental error" by introducing so many new flavours.

She said: "People are traditional - most of us, by nature, don't like change, and we actually quite like the status quo.

"Anyone who knows anything about consumers and brands could have advised Nestle that this was a bad move.

"It is like making blue mashed potato and expecting people to eat it, just because it is different. We generally love brands such as Kit Kat, Twix, and Mars - all of which have been around for decades.

"What Nestle should have done was concentrate on a really updated advertising campaign, keeping their 'Have A Break' logo, which is very distinctive.

"Now they have really messed up because not only have they changed the brand, they've changed the flavour of the Kit Kat."