Scarily, this latest attack occurred while police were on high alert investigating the Manchester bombing, and was carried out by a group rather than a lone wolf.
Three major attacks in under three months is a huge blow even for a populace that prides itself on a 'get on with life' resilience.
Both the latest terror attack and the Manchester bombing have landed smack in the British election campaign, with voting starting Thursday night NZT.
There are also wider implications.
The new attack in London also follows two major attacks in Baghdad, Iraq, and three in Kabul, Afghanistan, which have coincided with the start of Ramadan, the 30-day period of fasting and prayer.
Late in May, Isis (Islamic State) called on supporters to wage "all-out war" on the West during Ramadan with new terror attacks. Isis has used the start of Ramadan before to call for attacks - previous statements were linked to attacks in Orlando and France.
That doesn't necessarily mean Isis is behind the London attack. Assigning blame for attacks is difficult.
There are various militant groups in Afghanistan and Iraq, aside from Isis. There's a difference between an attack being centrally organised by Isis and carried out by a cell, to other attacks 'inspired' by Isis or foreign events.
The previous attacks in the UK this year have involved homegrown Britons, perhaps inspired by outside events and groups. Isis claimed the Manchester attack, but that does not mean the group was directly involved in organising it. Police have said Abedi seems to have mostly carried out the attack on his own.
However, analysts have warned for a long time that as Isis is squeezed by military setbacks in the Middle East and as European fighters return home, the group would try to lift flagging momentum with high-profile attacks.
Isis also faces fresh competition from al-Qaeda, intent on a comeback by pushing forward a son of former leader Osama bin Laden to win back younger extremists from Isis. Hamza bin Laden called for strikes against 'Jews' and 'Crusaders' 10 days before the Manchester bombing.
The use of vehicles in terror attacks in popular city areas - also a feature of terror strikes in Paris, Nice and Berlin - is a constant threat. It will not go away until more of these areas, which attract large crowds, are pedestrianised and protected by large security bollards.
US President Donald Trump has today responded to London by arguing in favour of his long-stymied travel ban. He tweeted: "We need to be smart, vigilant and tough. We need the courts to give us back our rights. We need the Travel Ban as an extra level of safety!"
The Trump Administration has asked the US Supreme Court to reinstate its ban on travellers from six mostly Muslim countries and refugees. Courts have blocked it.
Trump also tweeted: "Whatever the United States can do to help out in London and the U.K., we will be there - WE ARE WITH YOU. GOD BLESS!"
After Manchester, terrorism spiked as an issue in the British election campaign, with Labour leader Jeremy Corbyn linking attacks to British foreign policy. He was accused by Tory opponents of "justifying" terrorism. Old pictures of Corbyn with Sinn Fein members featured in the British press.
Conventional logic would have expected Prime Minister Theresa May to benefit with a boost in support after Manchester, but the general polling trend has been towards a tightening between the two main parties.
May began the campaign with an imposing lead of up to 20-points but that was down to an average of 8-9 points last week. Both main parties have drawn supporters away from the minor parties.
Today's polls showed the Conservatives ahead by a range of 1, 4, 6, 9, 11 and 12. Pollsters weight data according to key factors, including whether there is a 'shy' Tory vote and whether Labour can inspire a high turnout among young voters.
Will three attacks in a short space of time tip undecideds towards May, a former Home Secretary used to dealing with security, in the final days?
Corbyn is an unconventional prime ministerial prospect on security and foreign policy and that makes the next few days politically uncertain. A more traditional potential leader than Corbyn could have clung closer to May on security.
Then again, could Corbyn benefit from a desire to shake things up? Does the attack make May's 'strong and stable' pitch seem hollow? Or will there be a phlegmatic, 'there's nothing that can be done if someone's crazy enough' attitude?
A slight rallying-around-the-leader or 'now's not the time to change' effect is more likely. It is hard to believe there won't be an accumulative impact from three attacks, especially with the latest one so closely resembling the March massacre.
It was a tragic case of here we go again.
