The Metropolitan Police said the officer suffered non-life threatening injuries after the incident, in Edgware. Police were called to the address at 10.25am today after reports of a suspect in the garden of a house in Manor Park Crescent. On arrival they found a man in the garden, and after he was approach, the suspect stabbed the officer in the face with a pen.
The woman was taken to hospital where her injuries are still being assessed.
A 39-year-old man was arrested at the scene on suspicion of breach of bail in addition to offences against the officer including threats to kill and GBH. Police used a taser to detain him.
He too has been taken to hospital for treatment.
Roy Smith, BCU Commander for North West London, said: “Sadly this is yet another reminder of the risks faced by our police officers as they respond to calls for help from the communities of London.
“The men and women of the Met go to work each day not knowing the dangers they may face.
“They run towards danger to protect others and their everyday heroism is something all Londoners should be proud of.
“This officer was subjected to a vicious and unprovoked attack.
“These are our police officers and they have family and loved ones to return home to.
“They deserve not only our admiration but also support.”
(More to follow)