In the wake of the suicide bomb attack at a concert venue in Manchester, Newshour Extra this week is asking how major cities around the world can minimise the risk to their citizens from such atrocities. Owen Bennett Jones and his guests consider urban security, counter-terrorism, and the compromises different cities make between civil liberties and public safety.
Photo: an armed policeman and a soldier patrol the streets of London, 24th May 2017. Credit: Getty Images