Two police officers were injured in the line of duty while making an arrest in Ealing in the early hours of today, Tuesday 13 February.
The officers were on patrol in a marked police car in Acton High Street at about 02:25hrs when they saw two males acting suspiciously.
When the officers pulled up alongside them they ran off.
Officers pursued on foot.
As they tried to detain one of the suspects, a 17-year-old male, he became aggressive and head-butted one of the officers in the face [Officer 1].
There was a struggle as the officers continued to try and detain the suspect, which resulted in both officers receiving stab injuries to their hands.
More officers arrived on scene and the suspect was arrested on suspicion of attempted grievous bodily harm and possession of an offensive weapon.
He has been taken to a north London police station where he remains in custody.
Both officers received first aid at the scene and were taken to a north London hospital.
Officer 1 suffered facial injuries and a laceration to his hand. He has since been discharged from hospital.
Officer 2 suffered a stab injury to his finger and requires surgery. He remains in hospital.
Detectives from Ealing CID are investigating.
Ealing Borough Commander Chief Superintendent Paul Martin said: "This incident is a reminder of the dangers that police officers face on a daily basis while carrying out their duties protecting Londoners.
"Policing is by its very nature unpredictable - however no officer should be subject to such a violent attack.
"I have spoken with the officers who are in good spirits and we will support the officers and their families through this difficult time."
Any witnesses or anyone with information is asked to call Ealing CID on 101 quoting reference number 513/13FEB or Crimestoppers anonymously on 0800 555 111.