The extremist, who was shot dead along with two accomplices, after murdering seven and injuring dozens more in the attack, had access to tunnels under Parliament after he worked at Westminster tube station.
— Claire Phipps (@Claire_Phipps) June 6, 2017
Images have emerged of the 27-year-old in high-viz jacket and blue London Underground uniform in May 2016 at West Kensington station during his training period.
According to colleagues, the father of two, who was employed by Transport for London (TFL) for six months, also worked at Canada Water station in the Docklands.
Butt, who kept his extremists views from co-workers, despite having appeared in the Channel 4 documentary, The Jihadi Next Door, was sacked for poor attendance.
A former colleague told the Mail: “He went to Westminster, then Canada Water, then didn’t pass his probation period.
“It was well known that he had appeared in this extremist documentary — but he was asked to leave London Underground not because of that, but due to poor attendance.
TERROR IN LONDON – LATEST COVERAGE FROM YAHOO UK:
“We are now asking ourselves if he was planning something on the job? The intel he will have picked up about Parliament, and the movements of MPs travelling through the station, would potentially be of great value. Maybe he was planning some sort of spectacular there.”
They added: “He was a very quiet and unassuming guy. I spoke to him at length about life and his beliefs. He was definitely religiously observant, but seemingly no more than anyone else.”
This morning, security forces have defended a decision to downgrade an inquiry into Pakistan-born Butt, who lived in Barking, east London.
The two other perpetrators were not known to security services.
Metropolitan Police assistant commissioner Mark Rowley said an investigation into Butt began in 2015, but “there was no intelligence to suggest that this attack was being planned and the investigation had been prioritised accordingly”.
The inquiry was “prioritised in the lower echelons of our investigative work”, Mr Rowley added.
A man who says he knew one of the attackers has claimed he reported him to the anti-terror hotline two years ago.
He told the BBC: “He had a justification for anything for everything and anything.
“What happened after he reported him: ‘Nothing, absolutely nothing, they didn’t get back to me nor was he arrested or you know just picked up for any kind of questioning.
“He was thrown out of a mosque, maybe over a year and a half ago, his local mosque, because of his radical views.
“The Muslim community in general get a lot of criticism over how we don’t root out extremism in our community. I did my bit, I know a lot of people did but the authorities didn’t do their bit and that’s what’s shocking.”
A TfL spokesperson said: “Khuram Butt worked for London Underground for just under six months as a trainee customer services assistant, leaving in October last year.”