A Nigerian in the UK, that goes by the name John Onyenaychi, has been jailed for life while on licence from prison for attempted murder on two police officers .
Onyenaychi, described as one of Britain's most dangerous men, slashed PC Paul Madden's throat with a Stanley knife in front of terrified commuters near a bus stop.
The maniac lashed out at other officers and shouted: 'Let me finish him off.'
PC Madden, 23, collapsed with wounds to his neck, throat and face and would have died within three minutes through blood loss.
But he was spotted by Samad Tadjkarimi, 65, a retired heart surgeon who applied pressure to his neck to keep him alive long enough to receive emergency surgery.
Mr Tadjkarimi, who was doing his Christmas shopping in the area, had retired three weeks earlier. He said: 'It's very humbling that my intervention perhaps contributed to the outcome of possibly saving his life – a very brave young officer.
'It's my duty. I'm sure anyone in my profession would do the same.'
During his rampage in Ealing, west London, Onyenaychi stabbed Police Community Support Officer Piotr Dolata twice in the head as he tried to help. Mr Dolata, 27, needed 12 stitches.
PC Madden was also attacked and another PCSO, Steven Constable, was slashed twice but escaped serious injury because the thickness of his high-visibility jacket saved him.
Onyenaychi, of Stratford, east London, was found guilty of two counts of attempte
d murder, causing grievous bodily harm with intent, robbery and attempting to cause grievous bodily harm.
Judge Peter Beaumont, the Recorder of London, gave him two life sentences and ordered him to serve a minimum of 25 years after a nine-day trial at the Old Bailey.
Outside court Detective Chief Inspector John McFarlane said: 'He is one of the most dangerous men in Britain.'
Onyenaychi, who has committed violent offences since the age of 12, was out on licence from a two-year prison sentence for causing death by dangerous driving while high on drugs.
The attack on the three officers last December was the culmination of a six-day 'crime spree of lethal and extreme violence', said Brian Altman QC, prosecuting.
He told the jury that 6ft 2in Onyenaychi '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 Onyenaychi became agitated when challenged about his ticket on a bus in Ealing.
PCSOs recognised him by a distinguishing mark under his right eye as a man wanted for a previous attack.
When PC Madden arrived, he 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.
After an initial attack, he pulled the officer 'close in and, with force, cut him across the throat'. He stabbed PC Madden three or four times before colleagues were able to intervene.
Four days earlier, Onyenaychi stabbed a man five times, causing serious wounds, at a minicab office in Brentford, west London, after a failed robbery.
And two days before that, he stole a laptop computer from a man in Fulham, west London, after threatening him with a knife.
