On Wednesday afternoon, an unidentified man drove a car into a group of people on Westminster bridge, injuring more than 40 before making his way to the Houses of Parliament, where he stabbed a police officer who later died of his injuries.
The assailant did not get far before a police officer – in one of the country's rare moments – shot and killed the attacker.
The average police officer in the UK (barring Northern Ireland) does not carry a firearm.
What is an AFO?
If however, a police officer can prove that they require a gun, they go through stringent training and become Authorised firearms officers (AFOs).
In 2016 there were 5,639 AFOs, making up 4.4 per cent of all police officers, and in that same year there were 14,753 police firearms operations, 85 per cent involved with Armed Response Vehicles (ARVs).
What this means, is that when a police officer does discharge a weapon, it demonstrates the particularly serious nature of the incident.