Who was the Streatham attacker and why was he imprisoned?

Sudesh Amman, from Harrow in north-west London, was jailed in December 2018 after admitting to 13 counts of expressing his support for Islamist terrorism and possessing and sharing Islamic State and al-Qaida propaganda in a family WhatsApp group and on social media. He was 18 at the time.

Amman had come to police attention in April of that year for posting extremist material and was arrested a month later. He expressed support for Isis and sent beheading videos to his girlfriend, advising her to kill her “kuffar” (unbelieving) parents.

He also wrote about the desirability of conducting a terror attack: “If you can’t make a bomb because family, friends or spies are watching or suspecting you, take a knife, molotov, sound bombs or a car at night and attack.”

At the time of his conviction at the Old Bailey, acting Commander Alexis Boon, head of the Metropolitan police counter-terrorism command, said Amman had a “fascination with dying in the name of terrorism”, as seen in a notepad recovered from his home.

“Amman had scrawled his ‘life goals’ in the notepad and top of the list, above family activities, was dying a martyr and going to ‘Jannah’, the afterlife,” she said.

Why was he released?

Amman’s jailing for three years and four months was a fixed-term sentence and, in common with other terrorism offenders, Amman served half of it, taking into account time he had spent on remand before the trial.

He was released in January, but considered a sufficient threat to the public that he was released on what Whitehall sources said were “very stringent” licensing conditions, including a nighttime curfew plus active surveillance by undercover police.

Active surveillance is reserved only for the handful of most serious cases at any one time in the UK, but it was crucial in ensuring a rapid end to Amman’s stabbing spree.

Film and photographs of the attack in Streatham show Amman being apprehended and shot dead by at least two armed, plain clothes police officers within minutes of him having injured two people on the busy south London high street.

Could his release have been prevented?

The exact details about Amman’s imprisonment and release are not yet clear. He appears to have been on a normal, fixed-term sentence, meaning he would be eligible for release on licence halfway through the jail term.

Unless he committed further offences in prison there would be nothing to prevent his release – although he was clearly subject to a number of conditions in what turned out to be an unsuccessful attempt to prevent him being dangerous to members of the public.

Why was Amman shot? Is it legal for plain clothes officers to have taken action?

Police are allowed to use “reasonable force” to prevent crime. In the case of a terrorist attack, if an officer honestly believes someone poses a threat to their life, or to the life of others, firearms can be used.

The decision to shoot is the officer’s alone. For the shots to be legal, they must show they were acting in the defence of themselves or others and that their actions were proportionate. Official policy is that firearms “shoot to incapacitate” although they are trained to shoot in the chest, where it is likely the suspect will be killed.

Normally, armed officers arriving at a terrorist incident would be in uniform, but because of the unusual nature of Amman’s case he was being monitored by undercover officers carrying Glock pistols, intended for their own protection.

Armed officers of all types are allowed to self-deploy in an emergency situation, and are supposed to inform their targets – if possible – that they are police and may shoot. After any fatal shooting, as in the case of Streatham, an investigation by the Independent Office of Police Conduct is mandatory.