It was an agonizing explosion of unthinkable terrorist violence that lasted a few minutes, killed five people and destroyed dozens of lives. And it was, in several ways, an example of the new, low-technology terrorism that has plagued Britain in recent years.

On any given weekday, the scene around the Westminster Parliament Buildings is a tense and unpredictable mix: crowds of people, young and old, moving about with surprising freedom; multiple hardened layers of extremely well-tested and expensive security built after decades of even worse attacks; and a constant scattering of angry and unhinged men on the sidewalks and the square, some shouting slogans, some camped out for years, some appearing to teeter on the edge of violence.

On Wednesday, that scene introduced another now-familiar British element, one that has materialized during the past four years: the determinedly self-absorbed lone attacker armed with no more than a knife and a vehicle. The result was heartbreaking.

I’ve spent many long days in that space, between the Thames and Parliament Square, and on the sidewalk that runs along Westminster Bridge and past Big Ben, and always marvelled at its mix of workaday normalcy and high-tension security: A crowd of schoolchildren will pass, then some office workers going to the pub, then a team of security officers with assault rifles will appear from a concealed doorway and interrogate someone.

It’s a balance of freedom and security that’s the result of decades of attempts to attack the Parliament Buildings, including a bombing inside Westminster in 1974 that injured 11, another in 1979 that killed Conservative MP Airey Neave and a mortar attack on the prime minister’s residence at 10 Downing St., around the corner, that caused shells to explode outside John Major’s cabinet office in 1991.

In response, Britain has invested in a lavish and discreet system of concrete moats, high gates, security tunnels and stealth surveillance that surround Westminster today and theoretically make it impervious to such traditional high-explosive terrorist attacks.

In Wednesday’s attack, an unknown man circumvented those protections by employing the new, extremely low-technology form of terrorism that has flourished in Britain since 2013. It uses no more than knives and motor vehicles, and instead of attempting to breach secure symbolic sites, it kills people on the sidewalk in seemingly random attacks. And the men who carry out these attacks generally tend to be local, unstable and unaffiliated with movements or organizations, except through personal sympathies.

That was the profile of Michael Adebolajo and Michael Adebowale, young British men from Christian families in south London who, after becoming attracted to Islamic extremism, murdered and beheaded the soldier Lee Rigby on a crowded sidewalk in 2013; of Muhaydin Mire, a 29-year-old man from Leytonstone, East London, who – after becoming delusional and obsessed with Syria – attacked and seriously wounded three people with a seven-centimetre knife at his local Underground station in 2015.

It was also the description of Pavlo Lapshyn, a Birmingham graduate student and supporter of right-wing anti-immigration movements who stabbed an 82-year-old Muslim man to death on the sidewalk in 2013, and of Thomas Mair, a member of far-right and anti-immigration political parties who stabbed Labour MP Jo Cox to death in a West Yorkshire laneway in 2016, in what courts concluded was an act of terrorism targeting her for her opposition to the Brexit referendum.

These incidents marked a new wave of terrorism in Britain, ending more than half a decade during which terrorism had nearly vanished from Britain and much of Europe: Nobody had been killed in a terrorist attack in Britain between 2005 and 2013 (except a single 2017 event in Glasgow in which only the terrorist himself was killed).

The incidents during the 2000s tended to involve bombs and highly organized plots – they included a long string of deadly Irish Republican Army attacks in 2000 and 2001, and the July 7, 2005, London transit bombings which killed 56, including four suicide bombers.

Since 2013, though, terrorist attacks in Britain have generally involved men unaffiliated with terrorist organizations (except through personal sympathies) and weapons readily available around the house.

While the motive of Wednesday’s attacker is currently unknown, the nature of his attack seemed to point to the “lone wolf” Islamic-extremist attacks that have occurred in Europe in recent years, involving knives and motor vehicles. And his choice of target – random bystanders on the sidewalk and police guarding the Parliament Buildings – makes this part of a very disturbing recent British trend.

The Globe and Mail
Published Thursday, Mar. 23, 2017 5:00AM EDT
Last updated Thursday, Mar. 23, 2017 7:48AM EDT

Video: Raw video shows aftermath of two incidents near the British parliament