New footage has emerged of the final moments of the Streatham terrorist walking calmly along the street before stabbing two innocent people.
CCTV footage obtained by ITV News shows Sudesh Amman decked in a hat and coat and carrying a white bag just seconds before grabbing a knife from a shop and attacking a man and a woman.
Just one minute after his assault began, armed police, who had been trailing the convicted terrorist following his release from prison, shot the 20-year-old dead.
Wearing a fake suicide belt, Amman launched his attack in Streatham High Road, south London, on Sunday afternoon.
He was jailed for three years and four months for possessing and distributing terrorist documents in December 2018, then freed automatically halfway through his sentence before being placed under 24-hour surveillance.
Metropolitan Police commissioner Cressida Dick said Amman managed to stab two people while under surveillance because the operations are not "man-to-man marking”.
Britain's most senior police officer told the London Assembly police and crime committee that a time delay in responding would be "inevitable" if someone did something "totally unexpectedly”.
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Giving evidence to the committee on Wednesday about general tactics used by counter-terror police, Dame Cressida said: "They are conducting covert surveillance, so they are not of course providing man-to-man marking.
"They are there covertly and that is a deliberate thing.
"It is inevitable that there could be a time delay before somebody totally unexpectedly does something.”
The Daily Mail reported that up to 20 officers would have been involved in watching Amman.
Dame Cressida added: "I wish I could assure the public that everybody who poses a risk on the streets could be subject to some sort of thing that would stop them being able to stab anybody ever, but it is clearly not possible.”
A team of 75 officers is working to gather evidence for the coroner about Amman's rampage.
The Independent Office for Police Conduct watchdog is also investigating how he came to be fatally shot, as is standard when any police operation ends in a death.