Image caption Bottled water has become a profitable product that is sold across the world

In the last 40 years the bottled water industry has gone from a business prospect that few took seriously, to a global industry worth billions of pounds.

The commodity itself remains simple. The way we think about it has changed fundamentally.

Water is natural, pure and sourced at minimal cost. Its real value lies in its marketing and branding.

"I think bottled water is the most revealing substance for showing us how the global capitalist market works today," says Richard Wilk, professor of anthropology at Indiana University.

"In a sense we're buying choice, we're buying freedom.

"That's the only thing that can explain why you would pay money for a bottle of something that you can otherwise get for free."

Enormous markets

Image caption Consumers used to prefer free tap water to expensive bottled water

Through a confection of advertising and marketing, bottled water has become one of the biggest success stories in the modern food and beverage industry.

"The demand for bottle water has grown exponentially in the last few decades," says Dr Peter Gleick, author of Bottled and Sold.

"It's doubled, it's doubled again and it's doubled again.

"And the bottle water companies see enormous markets not just in the rich countries but also in the poorer countries."

'No actual variety'

Given that water is such a fundamental resource and a matter of life and death, and given that it is such an abundant commodity to many and so scarce to others, it has become emblematic of capitalism and trade in a way that other parts of the food and beverage industry have not.

"Some people think that bottled water is the high point of global capitalism, particularly the people in the bottled water business," says Charles Fishman, author of The Big Thirst.

"I think bottled water actually represents a kind of caricature of… the global economy.

"It provides people in the developed world with 20 or 30 varieties of something for which there is no actual variety."

Sceptical customers

Image caption Perrier used slick advertising to make bottled water fashionable

At the beginning there really was no variety and the bottled water phenomenon began with one brand.

Perrier was a triumph of advertising, creating a brand that was to define a generation.

At the heart of the campaign to make the brand popular was Richard Wheatley, of the Leo Burnett advertising agency between 1979 and 1994.

"Perrier popularised bottled water," he says. "It made it acceptable, more than acceptable, it made it… desirable."

But it was not an instant success.

When Perrier UK was looking to increase its sales in the early 1970's, it faced a sceptical public.

Is it immoral to build mega brands of bottled water while parts of the world are dying of thirst? Fiona Ellis-Chadwick, Senior lecturer, Open University Is water different to any other commodity?

Many questioned why anyone would buy water when you could get it free from the tap.

Faced with such obstacles, Perrier turned to advertising with a campaign that was to change our consumer landscape for ever.

"The water comes from France, of course, but the English and the French aren't that good friends," recalls Wenche Marshall Foster, former chief executive of Perrier UK.

"So we thought rather than saying this is from France we sold this much more vague feeling of oh it's French, Frenchness, Frenchness is good, it's chic, it's everything that we English maybe would like to be."

Trendy drink

The Eau campaign was a marketing coup and sales went through the roof from 12 million bottles in 1980 to 152 million by the end of the decade.

Image caption Getting enough water is a struggle for more than a billion people in the world

Perrier was no longer just a bottle of water. The marketing and advertising teams had established a crucial emotional link between the product and the consumers.

"Perrier became a badge," says Michael Bellas, chairman of the Beverage Marketing Corporation

"When you held a Perrier bottle up, it said something about yourself, it said you were sophisticated, you… understood what was happening in the world.

"It was a perfect beverage for the young up and coming business executives, the trend-setters."

Convenient packaging

Where Perrier went the rest of the industry jumped in and product ranges and brand proliferation followed.

Before long, the market in still water became extremely important.

In an age of instant gratification, still water in portable bottles provided what people needed, exactly when they needed it.

"People in general are more and more time pressed," says Mr Fishman.

"We don't cook our own meals any more, we eat prepared foods of all kinds.

"And there's nothing more appealing than a bottle of cold water at a moment when you're really thirsty.

"But I think bottled water is one of those products that on many occasions when people buy it, what they're buying isn't the water so much as the bottle. That is the package and the convenience at that moment."

Soaring sales

Image caption Consumers buy convenience rather than just water

When people bought this convenience, what they were really buying was Polyethylene Terephthalate, or PET, the single most important innovation in the industry's history.

Strong, shatterproof and a highly valued form of polyester, PET is a by-product of the oil industry.

It is now utilised in the packaging of everything from pharmaceuticals and soap, to ready meals.

In years to come, the environmental impact of PET would haunt the industry and raise questions about its very survival, but in the 1990s this was a revolution.

According to Mr Bellas it was behind the subsequent incredible growth of the industry.

"Starting with the introduction of the small premium PET waters, the category started to explode," says Mr Bellas.

"The bottled water industry before PET on the list of all beverage categories was number seven. With the advent of PET, water jumped… to the number two spot… behind carbonated soft drinks.

Health and wellness

In the late 1980s, the French brand Evian recognised the growing, wider health and fitness trend and exploited it to the full by marketing their bottled water the ultimate health and wellness product.

"Evian was sold as a beautiful person's drink," says Mr Fishman.

"The early Evian ads featured absolutely gorgeous people working out or just after working out in their sweaty and skin tight clothes.

"It was a way of saying if you want to be fit, if you want to be healthy, if you want to be attractive, drink Evian - and by drinking Evian you will be those things."

The link between bottled water and the health and wellness movement was a recipe for success.

Between 1990 and the turn of the century, global sales of Evian doubled from 50 billion to more than 100 billion litres a year.

For some, the choice and freedom is worth the price asked. For others, it represents the excess and inequality of the modern world; a world where nearly a billion people have no access to clean water at all.

"We cannot lose sight of the ultimate absurdity of the bottle water industry," says Mr Wilk.

"Here we have a world where people are dying of thirst, where people lack… the clean water to feed their children and we're spending billions of dollars and huge amounts of energy moving water from… people who already have it to other people who already have it."

As our consumer attitudes have changed, criticism of the industry has only intensified.

At the heart of the matter is what bottled water is actually made of, oil and water; the world's two most precious resources, in one neat package.

"The industry really wants to address these environmental concerns head on and it is doing everything it can to help resolve them," says analyst Richard Hall from Zenith International.

"It can only play a part in the wider picture, but it's certainly doing a lot to help deal with the problem. The environment matters to this industry because it's their future."

Consumers choose

By branding and marketing water, it has been transformed from something that many of us took for granted into a product that now makes billions for global multinational companies.

But like all products, its success is driven by consumer demand.

"Some people… want to consider the bottled water industry as a marketing trick foisted upon consumers," says Kim Jeffery, chief executive of Nestle Waters in North America.

"I wish I was that good or had that much money.

"That is not a marketing feed, that's consumers voting with their purchases and their pocket books. Consumers make that decision that day."

The Foods That Make Billions. Liquid Gold, BBC2 at 2100 on 23 November 2010.