Mohammed Chowdhury, 33, and Khan were among nine members of an al Qaida-inspired group sentenced in 2012 for plotting to bomb the London Stock Exchange and build a terrorist training camp in Pakistan.
Khan was automatically released halfway through his 16-year jail term and had been out on licence for 11 months when he launched an attack at a prisoner education event at Fishmongers’ Hall in November 2019.
The 28-year-old was shot dead by police after stabbing to death Jack Merritt, 25, and Saskia Jones, 23.
Chowdhury, from east London, was sentenced to 13 years and eight months in 2012 after being described as the “lynchpin” of the group who plotted to plant a pipe bomb in the toilets of the London Stock Exchange.
He spoke about carrying out a “Mumbai-style” attack at the Houses of Parliament or the London Eye and a handwritten target list found at his home listed the names and addresses of then London mayor Boris Johnson, the Dean of St Paul’s Cathedral, two rabbis, the American Embassy in London and the Stock Exchange.
Chowdhury was also handed a nine-month consecutive sentence in December 2015 after he was convicted of violent disorder in prison.
He has been recalled to prison three times since he was first automatically released in January 2018 but the Parole Board said on Monday that he has “managed to move away from extremism” and is suitable for release on licence.
Chowdhury could have been held in jail until February 2030 if he was not found suitable for a return to the community by a parole review.
His case was reviewed at an oral hearing in October last year and on Monday the Parole Board said: “After considering the circumstances of his offending and time on licence, the progress made while in custody and the evidence presented at the hearing, the panel was satisfied that Mr Chowdhury had managed to move away from extremism.
“It determined that he was suitable for release.”
His release was approved on conditions including living at a designated address, observing strict curfews and submitting to enhanced monitoring including GPS tagging, polygraph testing and measures to manage desistance from extremist behaviour.
He must also comply with limits to his contacts and activities, as well as restrictions on the use of electronic technology.
Chowdhury was first released on January 25 2018 but was recalled to prison around six months later on July 19.
He was released for a second time on October 3 that year on the direction of the then justice secretary when it was determined the recall was not justified.
Mr Chowdhury’s level of engagement and intent to engage in terrorist activity is now low, and… this would be unlikely to change providing his mental health remains stable
Chowdhury was again recalled on November 15 but re-released on June 25 2019 at the direction of the Parole Board after an oral hearing.
He was then recalled a third time on July 17 that year due to concerns about his behaviour.
The Parole Board said the there had been “no evidence to suggest he had committed further offences” but “given the circumstances, the panel found the decision to recall him to custody at this time had been appropriate”.
Despite concerns about his behaviour including violence since he was last recalled, the panel said he had been “helped with his mental health and he has been compliant with prescribed medication”.
“A professional assessment determined that Mr Chowdhury had since fully recovered,” the board said.
“The panel noted that the evidence before it demonstrated that Mr Chowdhury’s level of engagement and intent to engage in terrorist activity is now low, and that this would be unlikely to change providing his mental health remains stable.”
In oral evidence, the panel was told there was no evidence of any return to extremist behaviour and no further security concerns had been identified in prison.
The panel said Chowdhury had undertaken programmes “to address the underlying causes of extremist offending and ways of disengaging”, along with working with “professionals to better understand his faith”.
It also noted his “wish to lead a better life and to work with the professionals involved in his case”.