Cocaine use in the UK is now so common that traces can be found in drinking water.
Tests on tap water at four different sites found a metabolised form of the illegal drug, which showed it had already passed through the human body.
The levels were so low they posed no health risk. But being able to find traces in tap water, even after stringent purification processes, comes as a startling indication of how widespread drug use has become.
Past tests have found traces of cocaine on nearly every banknote in circulation, in toilets in the House of Commons and at two-thirds of Cambridge colleges.
Benzoylecgonine, the form of cocaine that is generated once the drug has been processed by the body, was discovered in lab tests by the Drinking Water Inspectorate.
It is the same compound that is searched for in urine-based drug tests for cocaine.
Public Health England analysed the findings and concluded that the trace amounts found in drinking water are not dangerous.
But Steve Rolles, from the drug policy think tank Transform, said the findings were an indication of the popularity of the drug in Britain today.
“We have the near highest level of cocaine use in western Europe,” he told The Sunday Times this weekend. “It has also been getting cheaper and cheaper at the same time as its use has been going up.”
Cocaine is the only major drug that has increased in use overall since 1996.
It costs around £40 a gram in Britain compared to as much as £115 in the US - largely because the purity of cocaine sold in the UK has fallen drastically in recent years.
In the 1980s and 1990s it was seen as a drug of the wealthy and fashionable, but is now taken by those of every class and profession – and even by schoolchildren.
The United Nations Office on Drugs and Crime estimates that one in 20 British teenagers aged 15 and 16 have tried cocaine.
The numbers treated for cocaine addiction in Britain rose from 10 770 in 2006-2007 to 12 592 in 2007-2008, the most recent figures available. Nearly 700 000 people aged 16 to 59 are estimated to take it every year.