By Lucia Binding, news reporter
A police officer who was stabbed in the head in a "frenzied" machete attack in east London is seriously injured but will recover, police said.
The patrol officer, who is in his 30s, was stabbed several times at around midnight after attempting to stop a van on Leyton High Road.
The vehicle's driver, a man in his 50s, failed to stop and then got out of the van and attacked the officer with the machete, police said.
Detective Chief Superintendent Richard Tucker said: "Having engaged the driver, who was quite aggressive… he then tries to make off, gets back in the van, and a violent struggle ensues where he produces a weapon and stabs our officer in the head and around the body."
While being stabbed, the policeman, who has around a decade of police experience, managed to Taser his attacker before the suspect was arrested by another officer.
The attacker was then arrested by another officer, who was not armed with a Taser.
DCS Tucker, who described the attack as "frenzied and unprovoked", said the officer is "seriously injured, but he will make a recovery".
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The officer, who is "fine" but "shaken up", has been commended for his bravery and is being treated for a stab wound to the side of his head, which required stitches, and an injured hand from fending off the attacker.
He was scheduled to undergo surgery on his hand at 10am, DCS Tucker said.
As Mr Tucker was briefing the media at Forest Gate Police station, the van which officers had stopped was taken away on a flatbed truck for further forensic examination.
The attacker, who did not require hospital treatment, was arrested on suspicion of grievous bodily harm and taken to an east London police station.
Metropolitan Police Federation Chairman Ken Marsh said: "This is horrific news. Police officers across London are out there every day at risk protecting the public – and sadly yet again a Metropolitan Police officer has suffered a severe injury on duty.
He added: "Enough is enough. Police officers should be going home at the end of their shifts. Not to hospital."
Home Secretary Priti Patel tweeted: "Absolutely horrified by the shocking stabbing of one of our brave police officers in Leyton overnight.
"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."
Police are not looking for anyone else in connection with the attack and there are no other reported injuries.