A Metropolitan Police (Met) officer has been dismissed for raping a woman in a police locker room.
The attack happened in March 2009 after the off-duty Pc took the drunk woman to St Pancras station in north London.
The victim complained but the Crown Prosecution Service ruled there was not enough evidence to press charges.
But a police misconduct hearing found the sex was "non-consensual". The Women Against Rape group said the decision not to press charges was "outrageous".
The woman, in her early 20s, had drunk several glasses of wine at a party at a hotel in central London and went outside when she began to feel unwell.
CCTV showed the police officer, who had been drinking in a nearby pub, starting to talk to the woman.
He then led her away from her party to nearby St Pancras train station where he was due to sleep in a locker room before starting work early the next day.
In interview he said during the night they had consensual sex.
When the woman returned home she told her friend she had little memory of the evening after leaving the party.
She said she recalled waking up to find a man having sex with her.
The matter was referred to the Independent Police Complaints Commission (IPCC), which managed the investigation and the evidence given to the Crown Prosecution Service (CPS).
A CPS spokesman said there was insufficient evidence to prosecute as it had to prove the offence had happened beyond all reasonable doubt.
But the Met's disciplinary hearing findings, based on the information gathered by the IPCC inquiry, are based on the balance of all probabilities, and found the police officer had non-consensual sex with the woman.
The IPCC refused to name the officer as he had not been charged with an offence.
IPCC Commissioner Rachel Cerfontyne said: "The actions of this officer will rightly appal the public as they have appalled me.
"His behaviour was in my view predatory and he exploited the vulnerability of a young woman.
"His conduct would be contemptible from anyone - from a police officer it is nothing short of despicable."
A Women Against Rape spokeswoman said: "This woman was very courageous. It is very difficult to report a police officer to the force that the rapist belongs to and we know of a lot of women who are too scared to do that.
"She has been determined and done a great deal of good."
Commander Mark Simmons said: "This officer acted in an intolerable way and it is only right that once such dreadful behaviour was found proven the man was dismissed."