PC Stephen Maskell, 44, based on the North East Command Unit, appeared at Willesden Magistrates’ Court on Thursday, 17 June.
He was found guilty of assault by beating and using threatening, abusive, insulting words or behaviour likely to cause harassment, alarm and distress to another person.
The charges relate to an incident in the early hours of the morning of 5 July 2020 in Charlton Road, NW10.
A disturbance was heard in the street and when a concerned member of the public, the victim, went to investigate, he was challenged and detained by PC Maskell.
PC Maskell was off duty at the time, however he identified himself as a police officer and grabbed the victim, shouting that he was detaining him for a search despite not having grounds to do so.
Maskell became aggressive and abusive to the victim and to another resident who came into the street to see what was happening. Officers attended and found Maskell clearly heavily intoxicated. He was arrested and later charged in August 2020.
The Met’s Directorate of Professional Standards was made aware of the incident and Maskell was placed on restricted duties. Misconduct proceedings will take place following the conclusion of criminal proceedings.
He will appear for sentencing before Willesden Magistrates’ Court on Monday, 19 July.
Superintendent Waheed Khan, North East Leadership and Support, said: “The high standards we expect from our officers apply equally when they are off duty.
“PC Maskell’s actions on this night were unacceptable. Misconduct proceedings will now take place following the conclusion of criminal proceedings.”