The sight of paramedics crouching over a body on Westminster Bridge while the Prime Minister is evacuated to safety and MPs are put under lockdown yards away in the Houses of Parliament is extremely chilling and harrowing.
But while the terror attack was designed to destabilise and panic the population the hard fact is that these types of opportunist atrocities using vehicles are the most difficult to defend ourselves against.
A person who decides to use a car or lorry as a weapon can wreak a terrible death toll on innocent people in any city in the world – as witnessed last July in Nice when 86 people were killed by a truck. We know that Islamic State has specifically called on its followers to use vehicles as weapons.
The vast majority of the time there is no intelligence to mark out the suspect, meaning they are free to roam, often appearing to operate like lone wolves with no need to talk to anyone to plan their attack.
Intelligence-led policing can work tirelessly towards safeguarding the nation but there are times when they are up against a faceless and anonymous enemy who can outwit them, not due to skill, but through cowardice.
Unfortunately, given the volatile nature of world politics which sees conflicts brought to our doorsteps rather than being contained in a war zone, there will be more such attacks, out of the blue, in any city or location.
There has always been the view that the United Kingdom is “lucky” because firearms are so restricted.
But yesterday’s attacker was only stopped from going on a killing spree because a police officer had a gun, and used it. Without that use of that weapon the situation would have been much worse.
The UK’s threat level for international terrorism has been ‘severe’ – meaning an attack is highly likely – since August 2014.
Perhaps now the time has come to seriously question the old and perhaps somewhat quaint tradition of having unarmed police officers on the streets of Britain. Having armed police on the street, with every officer carrying a gun, would not stop terror attacks but would mean we would have more professionally trained people able to bring such incidents to an end more quickly.
Yes, we have a long history of unarmed police, but this has been eroded in a number of areas with police carrying guns in locations such as airports and in Parliament.
Indeed a poll released last month by the Met Police Federation revealed that nearly half of its members believed the force’s firearms capability should be increased. Last year Police Scotland said it was to increase the number of armed police by a third after warnings the country could not cope with a major terror attack.
Of course no-one will forget the dreadful tragedy of the shooting dead by police of Jean Charles de Menezes, who was mistaken for a suicide bomber at Stockwell tube station in London in 2005.
But all in all we need to accept that the world is changing and seriously consider routinely arming police officers.