London is the cocaine capital of Europe - but only during the week, new research suggests.
When use of the Class A substance on weekends is also taken into account the city has been overtaken for the first time in three years.
The findings emerged in a study of drug concentrations in sewage in dozens of European cities across 18 countries.
Tests conducted in March showed the average weekday concentration of cocaine in London’s wastewater was 949.3mg per 1,000 people per day.
This was the highest level recorded across the research and a jump compared to the previous year, when it stood at 730.4mg per 1,000 people per day.
However, the concentration of cocaine in the English capital was lower at weekends, at 840.5mg per 1,000 people per day.
This was a fall compared to 2015 - and means London was out of tune compared to the continent as a whole, with levels rising sharply at weekends in most cities.
Weekend averages cover Friday, Saturday, Sunday and Monday, while weekday levels related to the other days of the week.
Across the whole week the average daily concentration for cocaine in London’s sewer waters was 894.9mg per 1,000 people per day - which was the second highest behind Antwerp in Belgium (914.8mg per 1,000 people per day).
It is the first time since 2013 that the research has not shown London at the top of the chart overall for cocaine traces, the Press Association writes.
The EU’s European Monitoring Centre for Drugs and Drug Addiction (EMCDDA), which published the results, said: “Traces of cocaine in wastewater indicate that cocaine use is highest in western and southern European cities, particularly in cities in Belgium, the Netherlands, Spain and the UK.
“The analysis points to very low to negligible cocaine use in the majority of eastern European cities.”
Separate figures published earlier this year suggested that powder cocaine use has risen among people from households with an income of £50,000 or more in England and Wales.
In contrast, use of the drug among those from lower-income households was either down or flat year-on-year.
In the new study wastewater was analysed for traces of four illicit drugs - amphetamine, cocaine, MDMA - or ecstasy, and methamphetamine.
In most cities, wastewater MDMA loads were higher in 2016 than in 2011, with sharp increases seen in some locations.
This may be related to the increased purity of MDMA or increased availability and use of the drug, according to the EMCDDA.
It is the first time the findings from the project, conducted by the Sewage Analysis CORe group Europe, have been released in the same year as data were collected.
EMCDDA director Alexis Goosdeel said: “Wastewater-based epidemiology has demonstrated its potential to become a useful complement to established drug monitoring tools.
“Its ability to deliver timely data on drug use patterns is particularly relevant against the backdrop of an ever-shifting drugs problem.
“By detecting changes in drug use patterns, both geographically and over time, it can help health and treatment services respond better to emerging trends and changing treatment needs.”