In this 2014 documentary film about British Islamists living and proselytizing in north-east London, you can see Khuram Butt, one of the London Bridge terrorists, participating in a prayer session in Regent’s Park during which a black Caliphate flag was unfurled. He was a supporter of the banned Islamist group al-Muhajiroun.

Also featured in this documentary is Siddhartha Dhar, a convert to Islam who later travelled to Syria to join the Islamic State. Dhar, 33, is suspected of becoming a masked public “executioner” for Isis. Despite being on bail for alleged terrorism offences, he was able to travel to Syria with his wife and four children under the noses of the security services.

Why are these grotesque individuals tolerated in the U.K.? How is it that they are allowed to hand out indoctrination pamphlets in the street, defy police, unfurl the Caliphate flag in a public park and declare that one day it will fly over 10 Downing Street??