The warning came as the UK government announced the terror threat is increasing in Britain in the wake of last week’s Spanish attacks that saw at least 14 people killed and around 100 injured in Barcelona and Cambrils.
Yannick Veilleux-Lepage of the Handa Centre for the Study of Terrorism and Political Violence at St Andrews University said terrorists would respond to the building of barriers to protect pedestrianised thoroughfares by adopting different methods.
Speaking to Scotland on Sunday, Veilleux-Lepage said: “The reality is that even if as a society we decide we are going to invest billions of pounds and put bollards or offensive vehicle mitigation techniques on every street where there are pedestrians...that’s fine.
“But what studies in terrorism show is that people engaging in these activities will simply change their technique.”
In recent months the world has been shocked by a spate of Islamic State (IS) inspired vehicle ramming attacks, notably the 2016 atrocity in Nice which resulted in 86 deaths and the attack on Westminster Bridge in London earlier this year that saw six deaths.
On Thursday, Barcelona was struck by a similar act of terrorism when a van was driven down the crowded Las Ramblas at the height of the tourist season. The repetition of such attacks has led to barriers and bollards being put up to protect areas where crowds congregate, including at Edinburgh’s Royal Mile during the Festival.
“The bollards are limited in the sense that they are going to help counter this particular technique and they are going to be effective up until the point that these groups innovate,” Veilleux-Lepage said.
He believes vehicle attacks will continue so long as they are seen by perpetrators as a feasible way of maximising casualties and are approved of by their followers.
But with action being taken to improve security in public places, Veilleux-Lepage says methods of attack used in the Israeli-Palestinian conflict, such as stabbing, will become more commonplace.
According to Veilleux-Lepage, the notion of vehicle-ramming had its roots in Israel, where barriers were built up to prevent it.
“What I believe will happen will be what we have seen in Israel,” he said. “Vehicle ramming was used and then that was securitised and now the majority of terrorist-related deaths are knife attacks. There is a concept of contagion where a technique is used and it is used successfully and it is replicated. We haven’t yet seen that with knife attacks. But if you start seeing a bunch of vehicle ramming attacks that don’t work – that will be the next step.”
Already there have been examples of this disturbing means of assault. In 2013 Drummer Lee Rigby was mowed down by a car driven by his attackers before being hacked to pieces with knives and a machete.
The Westminster Bridge attacks saw a knife used after a vehicle had rammed pedestrians, while Labour MP Jo Cox was shot and stabbed by a far right extremist. Predicting a time when knives become the terrorists’ weapon of choice, Veilleux-Lepage asked: “What do we do at that point? Do we install metal detectors at Nandos and Subway? You are stopping one technique and you are holding off, hoping terrorist innovation doesn’t catch on. Now the reality is that terrorist innovation will always be quicker and our response will always be reactive. The reality we need to recognise is that it is impossible for any government to keep us 100 per cent safe.”
Meanwhile, Security Minister Ben Wallace said the threat to the UK is increasing as IS loses battles and territory in Syria and Iraq.
Wallace said extremist Britons and other Europeans are either unable to get out to the region to join IS or have come home and are trying to inspire attacks here. The terror group has already lost its base in Iraq, Mosul, and is facing an international coalition-backed offensive in Raqqa, Syria.
Wallace told BBC Radio 4’s Today: “I think the threat is still increasing, partly driven by the fact Isis is collapsing in Syria and people are either unable to get out there to fight for Isis and so they look to do something at home, or also because people have come back and tried to inspire people with their stories and tales of the caliphate. I think those two things mean that the threat is to some extent increasing.”