I blame the pope. Not the new one. Not the old one either. But one called Leo XIII back in the 19th century. He didn't just take cocaine. He advertised it, appearing on a poster having awarded a Gold Medal to the manufacturer of the "tonic" he carried in a personal hipflask to fortify himself in those moments when prayer was insufficient.

There is, as we shall see, a direct line from His Cokiness to the news that more people in Britain have tried cocaine than anywhere else in the world, according to the announcement by the International Narcotics Control Board yesterday.

Some 6.8 per cent of UK adults admit they have tried cocaine, compared with 4.9 per cent of Spaniards, the second-largest proportion. Yesterday, four 14 and 15-year-old girls at a school in Crawley, West Sussex, were expelled for snorting cocaine in toilets before lessons, graphically illustrating how deep-rooted the drug's use is becoming.

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Now, 2 per cent of Britons regularly use cocaine - a level as high as in the US. Cocaine is now the chic world's favourite drug.

Of course, you could go back further than Leo XIII and blame the Incas. The original inhabitants of the area which still produces three-quarters of the world supply - Colombia, Peru and Bolivia - chewed the coca leaf for thousands of years.

Officially, coca was reserved for Inca royalty but as archaeological relics of sculptures and ceramics show, it was widely used for mystical, religious, social and medicinal purposes. It was chewed not merely for its stimulant properties - which warded off fatigue and provided the energy and strength necessary for steep walks in the thin air of their mountainous homeland - but as a kind of food, for there are vitamins and protein present in the leaves.

The conquistadors didn't like the look of it. Initially the Spanish invaders banned coca as "an evil agent of the devil". But then the incomers discovered that, without what the natives called their "gift of the gods", the locals could barely work the fields - or mine gold. Suddenly, coca was not only legalised but taxed, with the occupiers taking a tenth of every crop. Coca leaves were distributed three or four times a day to the workers during their breaks. And the Catholic Church began even to cultivate it.

But the leaves did not travel well, so only occasional supplies were transported to Europe, though tests on 17th century pipes found in Shakespeare's garden a few years back are said to have showed up cocaine residues - which would presumably explain the references to "eternal lines" in this most famous sonnet, or the constant use of the word "blow" in King Lear.

By the Victorian era, however, they were on top of the technology. In 1863 an Italian chemist named Angelo Mariani brought onto the market a wine called Vin Mariani which had been treated with coca leaves. He first tried his new tonic on a depressed actress. The results were spectacular. The ethanol in the wine acted as a solvent and extracted the cocaine from the leaves - creating a compound called cocaethlyene that hugely reinforced the impact of both drugs, much as it has in the systems of Kate Moss and her fellows.

Vin Mariani contained 11 per cent alcohol and 6.5 mg of cocaine in every ounce, which is presumably why Leo XIII gave it his gold medal. He was not the only one.

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Writers loved it. Henrik Ibsen, Émile Zola, Jules Verne, Alexander Dumas, Sir Arthur Conan Doyle were all mad for it. Robert Louis Stephenson wrote The Strange Case of Dr Jekyll and Mr Hyde during a six-day cocaine binge. Royalty were enthusiasts. Queen Victoria, King George of Greece, King Alphonse XIII of Spain, the Shah of Persia and US presidents William McKinley and Ulysses S. Grant all knocked it back.

The polar explorer Ernest Shackleton took a similar product in tablet form to Antarctica, as did Captain Scott with less happy results. Auguste Bartholdi said that if he had taken Vin Mariani beforehand he would have designed the Statue of Liberty several hundred metres taller. In addition to the general feeling of well-being it induced it was also said to be "a most wonderful invigorator of the sexual organs" - not a feature which is mentioned in the papal endorsement.

The world's best known coca drink, however, came later. A pharmacist in Atlanta named John Pemberton had made his own coca wine. But when Prohibition outlawed alcohol in the States he had to replace the wine in his recipe with sugar syrup.

He renamed it Coca-Cola: the temperance drink "offering the virtues of coca without the vices of alcohol" and marketed it as the perfect beverage for a "turbulent, inventive, noisy, neurotic new America." Pemberton's ads touted it as "an intellectual beverage" which was "one of the most delightful, cheering, and invigorating of fountain drinks." Very invigorating. Every bottle contained the equivalent of a little line of cocaine.

By that time, cocaine was being sold over-the-counter. In Sears & Roebuck in the US they were, in 1900, selling a Peruvian Wine of Coca which "sustains and refreshes both the body and brain ... may be taken at any time with perfect safety". Cocaine was widely used in toothache cures and patent medicines - one, Ryno's Hay Fever and Catarrh Remedy, was 99.9 per cent pure cocaine.

In London in 1916, Harrods were selling a kit described as "A Welcome Present for Friends at the Front" containing cocaine, morphine, syringes and needles.

What enabled all that was the development of a technique to isolate the cocaine alkaloid from the leaf. A method was perfected by a German PhD student named Albert Niemann which distilled a crystalline tropane alkaloid from the leaves of the plant. That refined version of the drug brought the user an exhilarating rush by, in effect, tricking the brain into thinking it's been furnished with something pleasurable.

Like heroin and nicotine it taps into the brain's natural reward pathways bringing an enhanced awareness, self-confidence, feeling of strength and sexual prowess.

The effect thrilled the greatest minds. Sigmund Freud in 1884 published Über Coca in which he wrote cocaine brings: "exhilaration and lasting euphoria, which in no way differs from the normal euphoria of the healthy person ... In other words, you are simply normal, and it is soon hard to believe you are under the influence of any drug ... Long intensive physical work is performed without fatigue ... This result is enjoyed without any of the unpleasant after-effects that follow exhilaration brought about by alcohol ..."

The more rapidly it is ingested the swifter and more dramatic the effect. So much so that Arthur Conan Doyle had Sherlock Holmes describe cocaine as "so transcendentally stimulating and clarifying to the mind that its secondary action is a matter of small moment". Or to use the more demotic speak of a modern-day crack user "it is like a whole-body orgasm".

But that intensity of experience completely outside the normal range of human experience has a cost. Nature, in the words of one reformed drug-taker, is cruelly parsimonious with pleasure. The greater the high, the greater the crash when the brain realises the trick that has been played on it. Over time, it takes a bigger or more frequent dose to reproduce the same high.

Moreover, various doses of cocaine can also produce neurological and behavioural problems including dizziness, headaches, movement problems, anxiety, insomnia, depression and even hallucinations.

Because cocaine stimulates the cells of the central nervous system and the cardiovascular system, in the hour after cocaine is used, the risk of a heart attack rises 24-fold. And many of Freud's patients, to whom he recommended cocaine for a variety of illnesses ended up addicted to cocaine too.

As the century turned, so did the tide of opinion on cocaine. Its addictive properties had become clear. Cocaine began to appear in literature as a vice. The pendulum swung in the direction of moral panic. In 1903 the American Journal of Pharmacy described cocaine-users as "bohemians, gamblers, high- and low-class prostitutes, night porters, bell boys, burglars, racketeers, pimps, and casual labourers."

An official from Pennsylvania's State Pharmacy Board testified that "most of the attacks upon the white women of the South are the direct result of a cocaine-crazed Negro brain."

In 1904, the manufacturers removed the cocaine from Coca-Cola. The US Government tried to compel the company to change the name of the drink but, after protracted legal argument, the name was saved. The Coca-Cola Company is still sensitive on the subject. Its museum in Atlanta still does not mention the beverage's legacy from the magic bush from Peru, even though the drink is still flavoured with an extract of coca-leaves from which the drug has been removed.

But it persisted among the smart set through the 1920s and 30s. For all Cole Porter's insistence "I'm sure that if I took even one sniff, That would bore me terrific'ly too" he was a user. So was the author William S. Burroughs and the actress Tallulah Bankhead who famously quip-ped: "Cocaine habit-forming? Of course not. I ought to know. I've been using it for years."

Even so, cocaine was, in the decades that followed, overshadowed on the black market by synthetic stimulants such as amphetamine. With the 'flower power' of the 1960s, marijuana and LSD became the drug of choice. Cocaine made a brief revival but Ecstasy, heroin, acid and speed were dominant. But in the late 1990s and early 2000s cocaine came back in the US with street sales topping an estimated $35bn in 2003. And, as the US market for the white powder became saturated, the dealers looked to Europe.

With the search for greater highs have come greater dangers. Cocaine that is smoked reaches the brain in about five seconds, giving a rush which is much more intense than taking the same amount of cocaine in through the nose. A solvent like diethyl ether can be used to allow the drug to be smoked "freebase".

But the technique is highly dangerous because the mixture can easily ignite, as fans of Richard Pryor may recall - he set himself on fire while attempting to freebase. It is also a technique that tempts the user to overdose, since the high continues for ten minutes but the peak of the freebase rush is over almost as soon as the user exhales the vapour.

The risk of spontaneous freebase combustion led users to develop the most lethal form of cocaine - known as devil's dandruff, food, rock or simply crack. Here the cocaine is cooked with ammonia or sodium bicarbonate to a pale brown colour. In that form cocaine is at its most addictive, more so even than heroin.

Cocaine is what pharmacologists call "highly reinforcing". Experiments with animals demonstrate this. When it is made available to mice they will administer it themselves. Indeed they will put up with electrical shocks, and give up food and water, to get the drug.

The evidence is that cocaine is about as addictive as alcohol but that more users - about 50 per cent - end up with an addiction problem. The trouble is there is no way to predict which 50 per cent - "everyone starts off using cocaine in a non-dependent fashion," says Dr Adam Winstock of the National Addiction Centre, "Nobody thinks they'll end up in a dependency unit in five years." Cocaine dependency develops after about three years of steady use. But while it takes about six months for someone to become addicted to heroin, it can take as few as six hits of crack cocaine.

There is a further danger. It comes from the mixing of drugs. Taken with alcohol, cocaine produces cocaethlyene in the liver, which both produces a greater euphoria and a higher risk of heart attack or respiratory arrest. Taken with heroin, in a mixture known as speedball or moonrock, the cocaine produces a rapid increase in heart rate but when that wears off, the heroin slows down the heart, risking total heart failure.

John Belushi and River Phoenix both died taking speedballs. Taken with low doses of ketamine, in a combination clubbers know as CK1, it diminishes the hallucinogenic and paralysing effects of K; taken with high doses, it kills.

Most recreational users reassure themselves they will not venture into these dodgier areas. They simply pass a china side plate lined with lines of white powder - " a row of sherbet soldiers" as one regular user put it - around the table after dinner as their grandparents would have circulated the port, or their parents might have passed a joint.

Many of them will take the same amount over extended periods and not become addicted.

They will be unlucky if they discover 25 per cent of the heart attacks in the 18-45 year-old age group are prompted by coke, nor will they probably discover just yet that regular cocaine abuse will make them seven times more likely to have a heart attack later in life than non-drug users.

But for some there comes a point when their recreation becomes a preoccupation and then an obsession. Most of their money will go on the drug. Most of their time will be spent thinking about how to get hold of it. Family, friends and workmates will become increasingly alienated by their behaviour. The journey to dependency is an easy carefree path. The one out of it can be a far more difficult uphill struggle.

In demand

Chewing coca leaves became widespread through South America three thousand years ago. The plant was believed to be a gift from God

* Restoration poet Abraham Cowley was the first to introduce cocaine into literature, with a 1662 work entitled 'The Legend of Coca'

* Merck, now one of the world's biggest pharmaceutical companies, began manufacturing cocaine in the 19th century as demand surged for tonics and medicines containing it

* Experiments with animals suggest that cocaine is the most powerful drug for creating psychological dependence

* Cocaine possession for anyone other than medical personnel was made a crime in 1916, following newspaper reports of 'drug crazed soldiers' fighting in the First World War

*Seven years ago, the drug cost around £70 for a gram. Now it sells for as little as £35

* 635,000 people used it in Britain in 2004, according to Home Office figures. Almost 100 people a year die in the UK as a result of cocaine use

* There are an estimated 79,000 crack users in the UK, up from 58,000 five years ago

* Cocaine is now the second most popular drug in the UK after cannabis, with usage doubling in the last seven years

* More than 20,000 tonnes of cocaine were seized by UK customs officers in 2004

* The world market in cocaine is estimated to be worth as much as $400 billion a year

* Five per cent of all British banknotes are thought to have been used to snort cocaine