It has emerged that one of three terrorists behind an attack on London Bridge on Saturday (local time) featured in a television documentary on Islamic extremism in the UK earlier this year.
Khuram Shazad Butt, who was shot dead by police after using a van and knives to kill and injure people, appeared in a disturbing scene from Channel 4 documentary The Jihadis Next Door in January.
Butt and two accomplices were responsible for killing seven people and injuring dozens more in the attack, and police revealed he was known to both them and spy agency MI5 as a terror threat.
The 27-year-old had made a habit of filming his confrontations with police and posting them online, and his role in The Jihadis Next Door was perhaps an indicator of his extremist tendencies.
In a scene near the start of the documentary, Butt is seen praying and listening to a teaching among a group of Muslims bearing a black Islamic flag described as "ISIS-like" by a policeman in London's Regent Park.
Afterwards, the policeman searches them after a member of the public reports their flag.
Butt was one of 3000 subjects of interest in terrorism investigations - but police said he was not perceived as a priority as they had no intelligence to suggest that he and his co-conspirators were planning a terror attack.
Police say significant resources go into their investigations into imminent terror threats, but they simply weren't aware that one was about to occur.
A second attacker identified on Tuesday (NZ time) was Rachid Redouane, aged 30, who also went by the identity Rachid Elkhdar and was not known to police. Redouane claimed to be Moroccan and Libyan.
Police said they are still working to establish the identity of the third attacker.