At approximately 14:40hrs on Friday, 7 August officers on patrol in The Concourse, NW9 carried out a section 23 stop and search under the Misuse of Drugs Act.
A 14-year-old boy [A] was arrested on suspicion of possession of cannabis.
As officers carried out the arrest, a group began to gather around officers and obstructed the police vehicle from leaving the scene.
Further police units attended.
A further two people, a 23-year-old man [B] and a 25-year-old man [C] were arrested on suspicion of obstruction of a constable.
The police vehicle left the scene and the group followed on foot to Colindale Police Station; a group of approximately 30 to 40 people remained outside the building.
A cordon is in place around the police station and a Section 35 dispersal order was authorised and further officers are supporting the dispersal of the group.
A 19-year-old man [D] was arrested on suspicion of assaulting a police officer.
A number of officers received minor injuries but did not require treatment.
We have not received any reports that members of the public or those under arrest sustained any injuries.
All four have been released under investigation.
Officers have carried out a search of the area where the 14-year-old was stopped. Thirteen bags containing cannabis were found.
Chief Superintendent Roy Smith, Borough commander for the North West BCU, said: “Whilst I understand that people may feel strongly about some police activity and arrests, interfering or obstructing officers at the scene only serves to inflame an already tense situation.
“Instead, I would ask people to use one of our many mechanisms for engaging and listening when the situation is calmer. This enables both sides to review things with a cool and steady head and in possession of the full range of facts.
“Even when well-intentioned interfering, or obstructing officers carrying out their lawful duties, can cause far more problems than it solves. I am committed to listening, learning and improving but my officers must also have the ability to carry out their duties safely and without fear or favour.
“I am also aware of a number of rumours circulating on social media that specifically relate to injuries sustained by those arrested and the nature of this arrest. I want to clarify that no-one who was arrested required medical treatment. Likewise, this arrest was not as a result of a raid or anything of that nature, this was part of a routine patrol in the area.”