“IT’S as easy as buying a drink from an off-licence.” That is how Ellen Romans, a recovering drug addict, describes picking up cocaine near where she lives in London. And today top-notch blow is much cheaper than it was five years ago, when she started using it heavily. David McManus, her treatment worker at Blenheim, a rehabilitation charity, agrees. Pubs and bars are “flooded” with the stuff. Dealers know that their product is no longer scarce. They are more tolerant of hagglers and are resorting to gimmicks, including Black Friday discounts, to boost sales.

The observations of Ms Romans and Mr McManus (not their real names) fit a countrywide pattern. There are signs that changes are afoot in the cocaine market. Though overall use has not increased, supply seems to have soared and dealers are offering a purer product.

One indication of growing supply is the volume of cocaine seized each year. Between 2010 and 2016 this doubled, to 5.5 tonnes, even as seizures of other hard drugs fell. Analysis of sewage by the European Monitoring Centre for Drugs and Drug Addiction suggests a similar trend. It found that the prevalence of substances the body produces when it breaks down cocaine has doubled in London in the past five years. In Bristol it has jumped by 60% since data collection started in 2014. This probably captures a rise in purity.

And though the use of powdered coke is stable, crack has become more popular. Modelling by academics at Liverpool John Moores University suggest that the number of users rose by about 10% between 2011-12 and 2014-15. These estimates rely on data from prisons and treatment centres, and are thought to be more accurate than surveys, which under-represent those most likely to develop crack dependency.

Data from the National Crime Agency (NCA) on small-scale drug busts show that cocaine purity rose steadily from 26% in 2011 to 44% in 2015. Crack saw a similar increase. This has not gone unnoticed on the street. Mr McManus says that punters looking for top-notch cocaine in London used to ask for “shine”. But that word has almost fallen out of use as quality has improved.

Surprisingly, average street prices have not budged, even though wholesale prices fell by 15% between 2014 and 2016. That is partly because cocaine has a known street price of £40 ($53) per gram, explains Lawrence Gibbons of the NCA. Raise it, and punters go elsewhere; lower it and they suspect an inferior product.

What is behind this abundance of high-quality cocaine? Britain’s import boom has been fuelled by changes elsewhere. Colombia has upped its production of coca, the crop used to make cocaine, from 49,000 hectares in 2012 to 146,000 in 2016, according to the UN. That is explained partly by the collapse in 2014-15 of the Colombian peso against the dollar, making exporting more profitable. Also in 2015, the government stopped aerially spraying coca fields with weedkiller. A third, unexpected factor was a peace agreement between the government and the FARC, a rebel group. The terms included money for farmers who switched away from coca. But this was known in advance of the deal being struck in 2016, and actually encouraged a bigger crop.

Another international factor is a fall in demand in America. RAND, a consultancy, estimates that the amount of cocaine hoovered up by Americans halved between 2006 and 2010. Many explanations have been put forward, such as users growing older and tougher measures against trafficking from Mexico. Whatever the reason, excess supply could feed Britain’s habit.

Developments closer to home may also play a part. One is Britain’s online-shopping fixation, which extends to drugs. The share of British drug-takers who sourced narcotics from “dark web” markets rose from 12% in 2014 to 25% in 2017, according to the Global Drugs Survey, an online study. Web-bought drugs tend to be purer because vendors fear that poor customer reviews, like those on Amazon, will hurt business. Energy Control, a Spanish think-tank, examined samples of cocaine bought online and found an average purity of 72%, compared with 48% for street-level stuff.

Anti-drugs laws in Britain may have inadvertently boosted coke’s potency, says Harry Sumnall, a professor of substance use at Liverpool John Moores. In 2015 the Serious Crime Act gave police new powers to seize chemicals used as cutting agents, such as benzocaine, a dental anaesthetic. Though MPs hoped this would disrupt supply chains, dealers short of cutting agents may just flog a purer product.

This may sound like good news for casual users, who get a better product for the same price. But some seem to be overdoing it. The number of deaths related to cocaine or crack in England and Wales jumped from 139 in 2012 to 371 in 2016, a sharper increase than for any other mainstream drug. Police worry about an associated rise in other crimes, such as shoplifting. And treatment centres, already under strain from spending cuts, will have to care for addicts. Better cocaine will only lead to more people getting hooked faster, says Mr McManus. He worries that, in a couple of years, his treatment centre in London will have a lot more clients.