Trying to stop drugs being taken in the pub toilet is no easy task for licensees.
Most drug taking in pubs is done in a toilet cubicle - traditionally a very private place. But clearly licensees have a responsibility in this area and if they are not seen to be taking the proper preventative measures, their licence could be at risk.
So how do councils approach pubs that have a problem?
To find out, I joined an investigation, with officers from Kensington and Chelsea Council.
The officers seem to appreciate it is a tough issue for licensees to deal with and take a relatively softly-softly approach with the pubs we visit.
"We have liked the way licensees are working with us to address this problem," says one of the officers, who wish to remain anonymous. "Our aim is to tell the licensee ways to actively try and stop it."
One solution they suggest is putting oil on flat surfaces to make it more difficult to snort drugs off them. Apparently some licensees have been known to use WD40 on the flat surfaces in their toilets to deter users - but this is not recommended because of the potential harm it could cause.
On this mission, we are visiting premises where traces of drugs were found on a previous visit around six months ago.
The licensees were sent letters telling them drugs had been found and that they must be seen to be doing something about it.
"We are looking at the measures they have taken," says one of the officers.
Interestingly, licensees are not obliged to allow the council to test their premises, but according to one officer "nobody has said 'no' in a year", out of 120 visits.
At our first pub, the assistant manager is accommodating and immediately points towards the toilets for a check.
Out come the swab cloths, the means for testing for traces of cocaine, the only drug being checked for. If the cloth turns blue, it's a positive test.
And it's a direct hit straight up as the swab changes colour after a gentle wipe over the top of a toilet roll holder in the gents.
However, there's no trace found after a thorough search in the ladies' toilet. More prevalent in the ladies'
I suggest this is fairly normal - evidence in the men's and not in the women's. But no - according to the officers, female toilets show signs of cocaine use far more often than men's. "Especially around sanitary bins," says one. The mind boggles.
Anyway, the assistant manager does not seem massively surprised by the discovery of drugs, but is handed an information sheet on how to deal with the issue in the pub.
On to the second venue, and the officers' claim about women's toilets being more of a hotbed for drugs proves true as the ladies toilet seats are apparently "caked in it", but only a small amount is found in the gents.
At the next venue, which is more upmarket than the previous two, there is a "strong, fresh presence" of cocaine, despite the warning notices on the wall.
The manager seems resigned to the fact and suggests that aside from putting signs up warning people against drug use and checking the toilets, there is little that can be done. It seems like a well run place, so the officers take a sympathetic view, but again hand out a list of advice.
At our final venue, it takes a while to find the manger but once she appears, she seems happy for the inspectors to get to work.
Her chirpiness is well-founded though, as both sets of toilets are clean of drugs. And this is surprising because the clientele are on the whole people in their twenties and thirties.
Overall it's been an eye-opening evening, that has confirmed that drug taking is still prevalent in pub toilets. But far from ignoring the problem, most licensees seem eager to work with the council to stamp it out.
But whether the problem will ever be eradicated while drugs such as cocaine remain illegal is, as ever, open to debate.
Ways to combat drug abuse in your pub:
• Put up notices informing that checks are being carried out and there is zero tolerance of drug use
• Regularly inspect toilets for illegal activity; use portable UV lights or swabs by staff to carry out checks
• Remove toilet seat lids
• Treat other flat surfaces with non-toxic substance such as Vaseline
• Regularly clean toilets and surroundings
• Use saloon-style half-doors or opaque glass doors to toilet cubicles to identify abuse
• Use CCTV in open parts of the toilets