The BBC said the details bore striking similarities to the attack on London Bridge on June 3, in which all three attackers Khuram Butt, 27, Rachid Redouane, 30, and Youssef Zaghba, 22, were shot and killed by police at the scene.
In a special report on Islamist-inspired extremism, researched over two years, the undercover journalist used Twitter to make contact with Birmingham-born jihadist and Isis recruiter Junaid Hussain.
Speaking through an encrypted messaging site, 21-year-old Hussain said he could help train the undercover reporter on how to make bombs from home.
When Hussain, from Birmingham, was killed by a US Army drone in the Syrian city of Raqqa in 2015, another recruiter made contact with Inside Out's undercover reporter to continue the conversation. He detailed a plot to assassinate a police officer, including how to obtain firearms and bullets.
Inside Out London's undercover reporter said: "In July 2016, we discovered that the terrorist organisation was touting on Twitter and Facebook for British Muslims to stage attacks at specific London locations.
"We began conversing with one of their recruiters, who then invited us to chat privately on a secret messaging site. The authorities were fully aware of our contact with the terrorist organisation."
- PA, AAP