As Britain absorbs the latest terror attack in London, many people will be wondering what has gone wrong, and what, if anything, can be done to prevent similar incidents reoccurring. These are all reasonable questions – but the challenges faced by the authorities are immense.

The London Bridge attack demonstrates once again that terrorists have a crucial tactical advantage. They choose when and where to strike from a near limitless supply of soft targets. They are also adept at exploiting the relative openness of democratic societies by blending in, only to betray their malevolence at the last moment, in the violence of the deed. The attack also shows a new pattern is emerging, following the Paris attacks of 2015: the leisure and night-time economy is now a target. The victims of these attacks are often younger people out enjoying themselves – perhaps because they are also seen to embody a decedent Western capitalist culture – and they are vulnerable to deadly attack from something as mundane as a car, van or truck.

This all raises a troubling question: is anyone, anything or anywhere now off-limits?

The difficulty is that while the authorities are generally very good at protecting specific sites – such as government buildings, critical national infrastructure or iconic landmarks – they cannot similarly protect every public space without putting the public in lockdown. By their very nature, crowded public places are easy to access, they are the soft underbelly of shared civic life.

On London Bridge, the open road allowed the van used by the attackers to build up a rate of speed to make the intended impact deadly. Introducing steel railings (as in some cross-walks) between traffic and pedestrians might be an effective preventive measure, but attackers wedded to this method only have to target one of the many other unprotected streets. And of course there are limits to how many railings one can introduce, not least on financial grounds.

Changing the physical environment to “design out” terrorism is one of the most prevalent measures in many Western cities. But so far, these interventions have been primarily focused on two types of threat: vehicle-borne bombs rammed into crowded places or detonated close by, and timed or remotely detonated bombs.

That’s why you often see bollards or (more pleasingly) planters positioned to make it harder to get near “high-value” targets such as government buildings or transport hubs. But the latest terrorist innovation – using cars and lorries to kill pedestrians – is less vulnerable to simple physical security measures.

It could have been worse

Despite the dreadfulness of the attacks, it could have been worse. This was a suicide attack rather than a suicide bombing. It looks as though the three London Bridge attackers didn’t copy the bomb making seen in Manchester. The suicide vests they wore were fake. Had they not been, the death toll could have been far higher.

Neither were they able to obtain firearms (reflecting the UK’s strict firearms controls), again limiting the lethality of the attack. Moreover, the window of opportunity for killing was only eight minutes – this is the time it took for the cavalry to arrive and shoot dead the attackers.

It also should not be forgotten that any group that uses suicide attacks by definition loses members. That’s a high price, and it means these sorts of attacks are hard to keep up over the long term.

‘Things need to change’

In her response to the latest attack, the UK prime minister, Theresa May, hinted at introducing yet more new terrorism offences (likely aiming to criminalise additional areas of preparatory and support functions). She also spoke of increasing sentences for terrorism offences and of bearing down on what she views as a fundamental problem: an “evil ideology of Islamist extremism” and the ease with which it’s transmitted online.

Notwithstanding the civil liberties costs, none of these approaches offer any easy answers either. Most obviously, the supposed deterrent effect of potential punishment is irrelevant to the most committed attackers, who are prepared to sacrifice themselves for their adopted cause.

Then there’s ideology. Islamist fundamentalism might be a central theme of these attacks, but it relies on particular interpretations of Islamic texts and the meaning given to particular passages and verses (such as sword verses) and the significance of key concepts (such as jihad). Various Islamic texts provide the resources for a number of different and competing readings.

In the absence of any sure means of establishing authorial intent, a plurality of interpretations, be they “moderate” or “radical”, can be made and defended. Indeed, this is one of the factors which accounts for the fractional and heterogeneous nature of the wider “Muslim world”. It follows then that Islamic doctrines can be used to justify either violence or non-violence.

Governments are still struggling to work out how they can effectively respond to this problem. As May’s Home Office itself noted in 2011, the British government also runs the risk of being seen as a “theological arbiter” in deciding theological doctrines.

It all adds up to a fiendishly difficult challenge – and meanwhile, as the London attack reminds us, public spaces remain uniquely vulnerable.

Kris Christmann, Researcher, Applied Criminology Centre, University of Huddersfield.

This article first appeared on The Conversation.