A 56-year-old man has been charged with attempted murder after a policeman was stabbed in the head with a machete in the early hours of Thursday morning.
Muhammed Rodwan will appear at Thames Magistrates' Court today, charged also with possession of an offensive weapon after the attack in Leyton, east London.
The injured officer remains in hospital in a serious but stable condition, after suffering stab wounds to the head and body.
According to his bosses he "will make a recovery".
The officer managed to taser his attacker despite being injured in the "sudden and brutal" assault which lasted just seconds.
Witness Muhammad Faisal, 31, said: "We saw someone lying on the road. Next to him was his police uniform.
"They were providing him assistance to his head. We didn't see the wound, but we saw a lot of blood."
Responding to the incident, London Mayor Sadiq Khan tweeted: "This sickening attack on a serving police officer is utterly appalling.
"The men and women who serve in our police force in London are the best in the world, and their courage and dedication is inspiring. I'm in contact with senior Met officers, and an arrest has been made."
And Home Secretary Priti Patel, said she was "absolutely horrified" by the attack.
She wrote: "His courage in the face of danger shows how police put their lives on the line to protect us every day. I wish the officer a full recovery & my thoughts are with him."