Supermodel Kate Moss will not be charged over claims that she took cocaine, prosecutors announced today.
The Crown Prosecution Service (CPS) said there was "insufficient evidence" to proceed.
A CPS spokeswoman said: "Following a detailed and thorough review of all the available evidence, the CPS has decided there is insufficient evidence to provide a realistic prospect of conviction against the model Kate Moss over allegations involving drugs."
She added that the Met had "conducted all reasonable inquiries" into alleged use and supply of drugs by Moss on the night of September 5 last year at a recording studio in Chiswick High Road, west London.
The decision was made despite a pledge by Metropolitan Police Commissioner Sir Ian Blair to tackle middle-class users of the drug.
He said the decision on whether to charge Moss would take into account her effect on "impressionable young people".
CPS London's director of serious casework Rene Barclay said there was an "absolutely clear indication" that Moss was using controlled drugs and providing them to others.
But the case highlighted a glaring loophole in the law on dealing with drug-takers.
Video footage of Moss's activities could not prove whether the substance was cocaine, ecstasy or amphetamine, Mr Barclay said.
These drugs are in different categories - Classes A and B - and therefore the prosecution could not proceed because the CPS must prove beyond reasonable doubt which category of substance was being abused.
"The film footage provides an absolutely clear indication that Ms Moss was using controlled drugs and providing them to others," he said.
"However, in the absence of any forensic evidence, or direct eye witness evidence about the substance in question, its precise nature could not be established."
He added: "Ms Moss declined to provide any explanation when interviewed, and the direct eye witnesses also declined to provide evidence.
"Expert analysis of the footage, however, narrowed the possibilities down to three particular drugs - cocaine, ecstasy or amphetamine.
"But these three substances fall into two different legal categories of controlled drugs.
"To obtain a conviction, case law establishes that the prosecution must prove beyond reasonable doubt the legal category to which the substance being used belonged.
"Proving that it was a substance belonging either to one or other of two different legal categories is not sufficient.
"Accordingly, as the available evidence fell short of establishing the necessary crucial facts, we decided that there was no realistic prospect of conviction and that a prosecution could not therefore be started."
He added: "This was necessarily a protracted investigation in view of the need to obtain crucial evidence through a court order, the absence of Ms Moss from the UK for some months and the need to complete all reasonable lines of inquiry."
Although ecstasy commonly comes in pill form, it can also be snorted as a powder, and while amphetamine powder is generally swallowed, it can also be taken by nose.
Moss's offence came to light when photographs of the drug-taking appeared in a newspaper.
A Scotland Yard spokeswoman said: "Despite all reasonable inquiries being pursued by the investigation, which included forensic examination of the scene of the alleged drug taking and investigation into the suspected supply network, we have been unable to provide sufficient proof of the identity of the substance depicted in the media photographs.
"It should be noted that this investigation was never solely into the actions of one individual but mainly focused on tracing the wider drug supply.
"There are always inherent difficulties in getting criminal proof in an investigation instigated in response to images of alleged drug-taking.
"Nevertheless, we have a responsibility to investigate allegations of drug use, but this should be seen in the context of the major and dedicated work that occurs on a daily basis into disrupting criminal networks involved in major drug supply."
During the course of the investigation, Paul Roundhill, 51, of Fieldgate Mansions, Romford Street, east London, was charged with possession of Class A drugs, she added.
Last month he pleaded guilty to the offence at Thames Magistrates' Court and was given a 12-month conditional discharge.
A second man, aged 22, accepted a caution for possession of a Class A substance, she went on.
Four other people, three men and one woman, voluntarily attended police stations to be interviewed but no further action has been taken against them, the spokeswoman said.
After the drug-taking pictures emerged, Moss issued a public apology and said she was taking steps to address her "personal issues".
In a statement released through her model agency Storm last September, she said she took "full responsibility" for her actions.
She said: "I also accept that there are various personal issues that I need to address and have started taking the difficult, yet necessary, steps to resolve them.
"I want to apologise to all of the people I have let down because of my behaviour which has reflected badly on my family, friends, co-workers, business associates and others."
She then spent a month in the private Meadows rehab clinic in Arizona, and returned to the UK in January after a 142-day self-imposed exile.