A knifeman described as one of the most dangerous men in Britain was sentenced to life today for trying to kill two police officers.

John Onyenaychi, 30, cut Pc Paul Madden's throat as people watched in horror.

He then lashed out with his knife at other officers who tried to restrain him, the Old Bailey heard.

He called out: "Let me finish him off."

Pc Madden's life was only saved by the quick thinking of a retired heart surgeon who was out Christmas shopping.

Samad Tadjkarimi, 65, also helped community support officer Piotr Dolata, who was also stabbed by Onyenaychi in Ealing, west London, last December.

Mr Tadjkarimi, who had retired from Harefield Hospital three weeks earlier, said today: "It's my duty, I guess. I'm sure anyone in my profession would do the same.

"It's very humbling that my intervention perhaps contributed to the outcome of possibly saving his life - a very brave young officer."

Pc Madden, 23, was taken to hospital by helicopter and received emergency surgery for injuries to his neck, throat and face. He was left with permanent scarring.

PCSO Dolata, 27, needed 12 stitches to his head.

Fellow PCSO Steven Constable was slashed twice but escaped serious injury because his high-visibility jacket saved him.

Onyenaychi, of Wise Road, Stratford, was found guilty of two counts of attempted murder, causing GBH with intent, robbery and attempting to cause GBH.

He was ordered to serve a minimum of 25 years for the attack on Pc Madden, and given a second life term with a concurrent minimum of 20 years for attempting to murder PCSO Dolata.

Onyenaychi refused to come out of his cell during the nine-day trial.

The Recorder of London, Judge Peter Beaumont, said Onyenaychi had not shown any remorse.

The judge added: "He used a knife on the face and neck of a police officer who was doing his job.

"Paul Madden would have died within two or three minutes - such was the loss of his blood - without the help he received from the passing retired doctor."

Onyenaychi was on licence at the time, having been jailed for two years for causing death by dangerous driving while high on drugs.

He had in the past attacked a prison officer using a pencil as a homemade weapon and committed violent offences since the age of 12.

After being arrested for the attacks on police, he let out a four-letter rant of obscenities at the woman magistrate who remanded him in custody.

Detective Chief Inspector John McFarlane said: "He is one of the most dangerous men in Britain."

The attack on the three officers was the culmination of a five-day violent crime spree.

Brian Altman QC, prosecuting, told the jury: "This defendant embarked on a crime spree of lethal and extreme violence.

"He is a highly dangerous individual who thinks nothing of carrying a knife on him, a tool of his trade, and uses it as a lethal weapon when he wishes to do so."

Mr Altman said 6ft 2in Onyenaychi became agitated when challenged about his ticket on a bus in New Broadway.

Soon support officers recognised him a man who was wanted for a previous attack, and who had a mark under his right eye.

Pc Madden thought Onyenaychi might be armed and tried to arrest him.

"Without warning, the defendant ripped his hands from his pockets and moved towards the policeman," said Mr Altman.

"In an instant Pc Madden felt he had been struck on the left side of his face.

"Realising he had been stabbed, Pc Madden attempted to stop the defendant striking him again - but the defendant pulled him close in and, with force, cut him across the throat."

The knifeman was seen to strike the officer three or four times, Pc Madden's head jerking backwards each time.

PCSO Dolata was stabbed twice in the head with the blade as he pulled the attacker to the ground.

A number of officers were needed to restrain Onyenaychi who had not wanted to give up the retractable Stanley-type knife.

Four days earlier, he stabbed a man five times, causing serious wounds, in a minicab office in Brentford, west London, after a failed robbery.

And two days before that, he stole a laptop from a man in Fulham, west London, after threatening him with a knife.

Mr Altman said: "He threatened to kill the man unless he handed over the laptop. He boasted ‘I do this for a living'."

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