Police visited a freed terrorist two weeks before he murdered two people in a knife rampage at a London rehabilitation event, a court has heard.
Conference attendees and staff chased him outside while armed with a narwhal tusk, a decorative pike and a fire extinguisher.
They tackled Khan to the ground on nearby London Bridge, before he was shot dead by armed police.
The 28-year-old was being monitored following his release from prison in December 2018, where he served a sentence for his part in an al-Qaeda inspired bombing plot.
A review ahead of the inquests into the deaths of Khan and his two victims heard that the agencies meant to be monitoring him had “no inkling” of the planned attack.
Jonathan Hough QC, counsel to the inquests, told Friday’s hearing that Khan was subject to regular management by probation officers and had been “under consideration by the security services”.
“Systems and procedures existed for managing and monitoring him, and it will be for further investigation whether any potential defects in the systems can be identified,” he added.
Henry Pitchers QC, representing Ms Jones’s family, asked whether police or probation officers involved with Khan “should have had an inkling” of his murderous plans.
Mr Pitchers said police officers made their last unannounced visit to his home in Stafford on 14 November, just over two weeks before the attack.
His flat was in darkness and Khan was not happy about photos being taken of his Xbox games and wanted to speak to his solicitor, the lawyer said.
He added that it was ”hardly a reassuring profile“ to know the terror offender was unemployed, living alone and that his ideological mentoring had stopped months before.A lawyer representing Mr Merritt’s family suggested there was already evidence of a ”systemic problem“.
Nick Armstrong questioned why the West Midlands Counter Terrorism Unit handed responsiblily for Khan to Prevent officers in Staffordshire.
The Prevent programme was designed to stop people from being drawn into terrorism, rather than dealing with people who have already committed offences.
Mr Armstrong said: “In this case already on the material that has been produced, we have all the Prevent officers from Staffordshire saying they had no specific training in handling terrorist offenders.”
A lawyer representing the Independent Office for Police Conduct said the watchdog was investigating Khan’s contact with Prevent officers in Staffordshire, and the police shooting on London Bridge.
Danny Simpson said that although the two probes continued, there was “no realistic prospect” of either resulting in criminal proceedings against officers.
The court heard that Khan was given permission to attend the event organised by Learning Together, a programme linked to the University of Cambridge, and was not escorted by police.
“It wasn’t somehow slipping between the terms of his conditions – he was given express permission to attend,” Mr Pitchers said.
“Those who did give permission did nothing further to notify the City of London police, the Fishmongers’ Company where the event took place, nor the organisers of Learning Together.”
There were no security checks or metal detectors at the venue, the court heard, and Khan was able to walk in armed with two knives and wearing his fake suicide vest.
Mr Merritt was a coordinator for Learning Together and fellow Cambridge University graduate Ms Jones had volunteered on the programme.
Two other women, named in court as Isobel Rowbotham and Stephanie Szczotko, were injured in the attack but survived.
A toxicology test later showed Khan had been an occasional cocaine user in the period before his death, the Old Bailey was told.
A full inquest, due to start in April, will examine how the terror attack unfolded and if it could have been prevented.
It was the first of four alleged terror attacks carried out by serving or freed terrorist prisoners in England over the past year.
Khan’s family were attempting to have the inquest into the terrorist’s death be run together with those of his two victims, but dropped the argument on Friday amid resistance from bereaved families.
Mr Pitchers said it would be a “source of real, significant and persistent distress throughout the course of the inquest” if the coroner allowed involvement on behalf of Khan’s mother Parveen Begum.
Her lawyer Jude Bunting told the court she was “deeply shocked” by the Fishmongers’ Hall attack and offered her sympathies to Mr Merritt and Ms Jones’ families.
Mr Bunting said the family were “not aware of Usman Khan’s mindset or intentions”, adding: “As a mother herself, Mrs Begum still finds it hard to believe such terrible damage could be caused by her son.”
Mark Lucraft QC, the chief coroner for England and Wales, is to rule on a separate application by Khan’s family to be declared an “interested party” in the victims’ inquests.
Mr Bunting said they wanted to ensure “lessons are learned” but have no intention to attend the inquests unless called as witnesses.
Mr Hough recommended that the Khan family be allowed to ask questions upon request, but not be granted interested party status because of “legitimate concerns” by the victims’ families.
The ruling will be made by the coroner at a later date.