IT has happened like this before and it will happen again: people are out and about, having a drink, or a meal, or just walking about the streets when suddenly they are struck by terrorism in its rawest form: three men in a van driving at people before getting out and stabbing as many as they can. It is brutal and shocking and always will be, particularly because most of us can easily imagine ourselves in the ordinary situations in which the terrorists strike. But after three attacks in Britain in three months, the latest London atrocity is more than shocking – it is darkly and disturbingly familiar.

The precise details of the London Bridge attacks will take some days to emerge, but a few things are already clear. The attackers demonstrated incomprehensible cruelty and cowardice in targeting people on the street, but, like the Manchester bombing two weeks ago and the Westminster attack in March, the extreme situation also brought out the best in people, with the staff in the pubs and bars, the police, and people who just happened to be in the area demonstrating great personal bravery. The police were also on the scene in minutes and had killed the attackers within eight. Whatever else happens, it is proof that the emergency response in central London is almost as good as it could ever be.

However, effective though the response was, this weekend’s attack is also a warning for the future - not only because attacks of this nature are incredibly hard to prevent but because they are precisely the kind of random, low-tech terrorism that has been encouraged by Islamic State (IS). Attacks like the one in Manchester are relatively rare because it requires some degree of technical ability to build an explosive device, but IS encourages attacks like London Bridge and Westminster because it will always be easy to acquire a van or a car and a knife. Indeed, the British security services say that in the last four years they have thwarted 18 attacks that were similar in intent to Westminster.

In her response to the attacks, the Prime Minister Theresa May said enough was enough and that the evil ideology of Islamist extremism had to be tackled once and for all. She said the recent attacks represented a new trend in terror, and that, while they might not have been connected by common networks, they were related by the fact that they were copies of each other. Mrs May also singled out the internet as a place where extreme ideology is given a safe place to breed. “We need to work with allied democratic governments to reach international agreements that regulate cyberspace to prevent the spread of extremist and terrorism planning,” she said.

In the language she chose to use, and the details of the action she proposes, the Prime Minister’s speech represents a considerable toughening-up of the Government’s response to terror, and while some will worry that it could lead to draconian measures against internet freedom, she is right to identify it as one of the major battlegrounds. Terrorist plots end on the street, or in a concert hall, but they often begin online, where jihadists are almost completely free to recruit those who are willing to carry out attacks. It is an almost total freedom to hate that we do not accept anywhere else in society.

In response, internet providers and social media platforms have largely avoided responsibility, and for a long time sites like Facebook appear to have operated outwith the normal rules that would apply to publishers or broadcasters. However, they must now do more to block users who post extremist content and report anyone who appears to be contemplating, planning or supporting a terrorist attack. There are technological problems to tackle – and muting terrorism online is not the same as ending it in reality when the terrorists can find new ways to plot. It is also important to balance the risk of terrorism against the right to freedom of expression, but that is a balance which other parts of society manage to strike without encroaching on the important right to say what we want within reason.

In the wake of the Manchester attack, Mrs May has already won support from fellow G7 leaders for doing more to tackle online extremism – and it is a welcome first step, but there will also have to be much greater sharing of intelligence if Islamic-inspired terrorism is to be defeated. The Government is also looking again at its Prevent strategy, which has been greeted with suspicion by many Muslims. Mrs May says she wants to see an end to segregated communities, but the problem will be how to define the “extreme” elements that are considered outwith society and those that are considered safe.

In the meantime, when the cordon around the London Bridge area is lifted, the life of the community will start up again, as it did after Westminster. It is clear now that the aim of jihadists is to attack soft targets such as bars and music venues – anywhere where people are gathered and where the most havoc can be wreaked. But, even with three attacks in three months, the risk will always be minimal; and in the days to come, Londoners will deliver the ultimate riposte to terrorism: they will carry on as normal.