At around 13:50hrs on 23 September, police officers attended an industrial area in Dale Close, Barnet, to execute a drugs warrant as part of a proactive operation. As they executed the warrant, officers were injured by a suspected corrosive substance believed to be sulphuric acid.

Eleven firearms officers were believed to have suffered injuries related to a chemical substance and received medical treatment before going to hospital. However none were believed to be in a life-threatening condition.

London Ambulance Service and London Fire Brigade were also in attendance and four people other than the officers were also treated at the scene. The London Ambulance Service also dispatched its hazardous area response team (HART).

The Metropolitan Police’s Directorate of Professional Standards have been informed as is routine.

Four males were arrested on suspicion of Class B drug offences and causing grievous bodily harm against officers. One of them remained in hospital for treatment to burn injuries. Officers remained at the scene while enquiries continue. The incident was not being treated as terror-related.

Chief Superintendent Roy Smith – BCU Commander for Harrow, Brent and Barnet – said: “I am extremely grateful to colleagues from our Specialist Firearms Command who put themselves at risk to protect our communities, and colleagues from London Fire Brigade & London Ambulance Service who came to their assistance using our well established protocols for dealing with this type of incident.

“I’d like to reassure the local community that there is no ongoing risk to the public and local officers will remain on patrol in the area to provide reassurance.”