In the wake of a series of horrific lone actor attacks across the UK, calls have grown louder for the government to rethink how the law defines terrorism. The debate has been reignited by the stabbing of 10 people on a train at Huntingdon earlier this month, an attack with all the hallmarks of a mass terror event but, crucially, no apparent (at the time of writing) ideological motive. The alleged perpetrator has been charged with multiple counts of attempted murder, not terrorism.
To many, that distinction feels academic. After all, the victims are no less traumatised, the violence no less shocking. But in law, the difference matters profoundly. And as tempting as it may be to broaden the definition of terrorism to capture such acts, doing so would be a serious mistake, one that risks eroding the clarity, purpose and proportionality of counterterrorism law itself.
Why ‘ideological motivation’ matters
Under section 1 of the Terrorism Act 2000 (TA 2000), an act qualifies as terrorism only if it is carried out for a political, religious, racial, or ideological cause, and is intended to influence government or intimidate the public. This requirement of ideological intent is not an arbitrary technicality; it is the cornerstone of how terrorism is distinguished from other forms of violent crime.
Terrorism, by design, is more than violence; it is violence deployed for a collective purpose. It targets not just individuals, but the social fabric, attempting to terrorise a population, destabilise the state, or advance a cause. By contrast, the motives of most lone actor attackers are more personal: anger, resentment, isolation or a desire for notoriety. However devastating the results, such acts are not always defined as ‘terrorism’ in the legal sense because they are not meant to change society; they are, tragically, expressions of private rage.
Expanding the definition of terrorism to include every large-scale act of violence would blur this vital distinction. It would risk transforming terrorism law into a catch-all tool for any extreme act, eroding the precision and intent that make it a legitimate and proportionate instrument of national security.
The rise of the lone wolf
In recent years, the UK has witnessed a disturbing rise in so-called ‘lone wolf’ violence, attacks carried out by individuals acting alone, often radicalised online or inspired by previous atrocities.
High-profile cases such as Axel Rudakubana’s (pictured) Southport attack and Nicholas Prosper’s foiled mass shooting have exposed the limitations of existing law and intervention systems.
Rudakubana, known to the government’s Prevent programme, slipped through the cracks because his violent tendencies were not seen to be ideologically driven. Prosper, who murdered three family members and planned what could have been the largest massacre on UK soil, could not be prosecuted under terrorism laws because his motive was fame, not ideology.
These cases illustrate a troubling legal gap as to how lone wolves are identified and subsequently dealt with, but they do not prove that the definition of terrorism is wrong. They show that the framework for dealing with non-ideological mass violence needs strengthening, without collapsing the boundary that separates terrorism from other forms of serious crime.
Dangers of diluting the definition of terrorism
In his 2024 review, Jonathan Hall KC, the Independent Reviewer of Terrorism Legislation, warned against expanding the definition of terrorism to cover all forms of mass violence. Doing so, he argued, would ‘treat every violent eccentric as a potential terrorist’ and ‘skew the threat level’ in ways that could distort the allocation of security resources.
If every mass attack, regardless of motive, were classed as terrorism, the already stretched counterterrorism apparatus would be forced to monitor and investigate cases far outside its intended remit. Counterterrorism policing is designed to address coordinated ideological threats to national security, not to manage the complex and varied causes of individual violent behaviour, mental illness or social alienation.
A new offence
Rather than redefining terrorism, Hall proposed a more precise solution: a new criminal offence targeting individuals who intend to kill multiple people and prepare for such an attack, regardless of ideology.
This approach, now reflected in the government’s Crime and Policing Bill 2025, plugs the current gap without eroding the definition of terrorism. It allows authorities to intervene earlier and prosecute lone actor mass violence with the same gravity as terrorism, while maintaining conceptual clarity between ideological extremism and other forms of violent threat.
The bill also introduces complementary reforms, such as the Youth Diversion Order, designed to identify and redirect young people displaying early signs of extremist or violent behaviour. These measures represent a pragmatic, proportionate response to a changing threat landscape, recognising the need for modernisation without sacrificing legal precision.
Need for clarity and proportionality
At first glance, keeping lone actor violence outside the definition of terrorism may seem like a mere legal technicality. But in practice, it safeguards something fundamental: the integrity of our justice system.
If we start calling every lone killer a terrorist, the word itself begins to lose meaning. The law in respect of terrorism was designed to protect the public from organised, ideologically motivated threats such as groups and movements that aim to destabilise nations or societies. Its exceptional powers and heavy penalties are justified only because the crimes it addresses are, by nature, exceptional.
By maintaining the current definition, not only is the conceptual clarity of terrorism law preserved, but also the proportionality of state power. The answer is not to stretch the definition until it fits every tragedy, but to build complementary legal tools that address new realities without dismantling old principles.
Conclusion
Lone actor mass violence is one of the most pressing public safety challenges of our time. It demands urgent action, better coordination and stronger early intervention. To label every act of extreme violence as ‘terrorism’ may offer short-term public opinion satisfaction, but risks long-term legal confusion and overreach. The ideological requirement within the TA 2000 was not a loophole; it was a safeguard, ensuring our most powerful laws remain focused on threats to society as a whole, not every tragedy inflicted by a single, desperate individual.
By resisting the urge to conflate all violence with terrorism, we preserve a system that is both principled and practical, one capable of addressing evolving threats without surrendering its moral and legal foundations.
Claire Cross is a partner and Eve Campbell an associate at Corker Binning, London
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