The man who killed two people in a terror attack in central London has been named as 28-year-old British national Usman Khan.
Khan was released from prison on licence last year after serving eight years in jail for his part in another terror plot.
Here's what we know about him.
An Al Qaeda-inspired plot to bring terror to Britain
Khan was one of a group of nine people jailed in 2012 for plotting to bomb the London Stock Exchange and start a terrorist training camp in Pakistan-controlled Kashmir.
Khan and his accomplices Mohammed Shahjahan, 27, and Nazam Hussain, 26, were convicted of planning to set up the terror camp, while the other men in the group were convicted in relation to the Stock Exchange plot.
All nine said they were inspired by slain Al Qaeda leader Anwar al-Awlaqi.
Khan was sentenced to an indeterminate period in prison, with a minimum of eight years to be served.
His sentence was backdated to the time of his arrest in 2010, and he was released on parole in December 2018.
The trial judge, Justice Wilkie, labelled Khan and his two accomplices "the more serious jihadists" among the group, and said they should not be released until they were no longer a threat to the public.
"In my judgment, these offenders would remain, even after a lengthy term of imprisonment, of such a significant risk that the public could not be adequately protected by their being managed on licence in the community, subject to conditions, by reference to a preordained release date," Judge Wilkie said in 2012.
Justice Wilkie said the planned terror camp, which Khan wanted to run on land owned by his family, would have produced recruits who could "return to the UK as trained and experienced terrorists available to perform terrorist attacks in this country".
The men gathered in parks in a bid to make surveillance difficult and talked about leaving homemade bombs in the toilets of London pubs.
But the conspiracy was stopped by undercover anti-terror police before firm dates could be set for attacks.
During the case, prosecutors said police found a handwritten target list at the home of one of the men that included the Stock Exchange, the US Embassy in London, and then-mayor of London and now Prime Minister Boris Johnson.
According to British media reports, Khan was required to wear a tracking device after his release.
On Friday, he was reportedly invited to attend a prison education conference being run by Cambridge University criminology experts at London's Fishmongers' Hall.
He reportedly began stabbing people inside the historic building.
The Learning Together conference was to have brought together academics, criminal justice campaigners and others.
