The Telegraph reports that terrorist Khuram Butt, also known by the nickname Abz, appeared in a television special called “The Jihadis Next Door” last year (see it below):

He appeared in a television documentary last year about British extremists called The Jihadis Next Door, and was filmed at events attended by two notorious Islamic preachers.

As part of a year-long undercover documentary that aired last January, he was filmed attending one event alongside Mohammed Shamsuddin, who has warned that “Sharia is coming to the UK” and that the black flag of Islam will fly over Downing Street.

Shamsuddin said that his views were “moulded” by the hate preacher Omar Bakri – the Tottenham Ayatollah – who is now in jail in Lebanon for supporting terrorism…

In the Channel 4 documentary, Shamsuddin was filmed praying with a group of followers including one of the London Bridge attackers in London’s Regent’s Park under the black flag of Islam.

ABC News also is also reporting that Abz appeared in the documentary and says that, according to neighbors, he was part of a group led by Anjem Choudary. In a separate report at the Telegraph, two different people, including a former friend, say they specifically warned police one of the terrorists had become radicalized long before this attack (Note: I believe this is also about Abz but the story doesn’t name him):

The friend told the BBC’s Asian Network that the terrorist had been radicalised watching videos of the infamous American hate preacher Ahmad Musa Jibril.

He said: “We spoke about a particular attack that happened and like most radicals he had a justification for anything and everything and that day I realised I needed to contact the authorities.”

He added: “He used to listen to a lot of Musa Jibril. I have heard some of this stuff and its very radical. I am surprised this stuff is still on YouTube and is easily accessible. I phoned the anti-terror hotline. I spoke to the gentleman. I told him about our conversation and why I think he was radicalised.”

However, he said he was not arrested and was allowed to keep his passport. “I did my bit, I know a lot of other people did their bit, but the authorities did not do their bit,” the friend said.

An Italian woman living in the neighborhood had contacted local police two years ago after her young children spoke to the same man in a park and came home saying they wanted to become Muslims. This BBC report indicates that there was an investigation into Abz starting two years ago but that “there was no intelligence to suggest that this attack was being planned and the investigation had been prioritised accordingly.”

Here’s the Jihadis Next Door special from January 2016. The scene showing a group praying with the blag flag starts at 15:00. I can’t confirm which individual is Abz, but this report at the Sun claims to identify him.