Instant Arming vs Offensive Weapons: Where Does the Law Draw the Line?

Oct 27

When does an everyday object become an offensive weapon? Can security officers use improvised objects to defend themselves during a terrorist attack? And how can venues protect their staff without crossing the legal line?

By Sean Keelan | Blue Light Security Solutions Ltd

"Can we hide weapons around the venue in case of a terrorist attack?"

Some time ago, I was approached by the owner of a large venue who wanted to discuss his concerns about the threat of terrorism.

He was particularly worried about the vulnerability of his security officers.

Like the overwhelming majority of private security personnel in the United Kingdom, his officers were unarmed.

His concern was understandable. If someone entered the venue armed with a knife or another weapon, what could his security team realistically do to protect themselves and the public?

He proposed what he considered a practical solution.

Could we strategically conceal weapons around the venue, allowing security officers to retrieve them if a terrorist attack occurred?

He wasn't suggesting that security officers should routinely carry weapons. His intention was to provide them with something they could use if they found themselves confronted by an armed attacker.

I understood his thinking.

But I had to explain why deliberately positioning weapons around a publicly accessible venue was a very different proposition from a security officer using an everyday object to defend themselves during an immediate attack.

It led to a discussion about two concepts that are often misunderstood: instant arming and offensive weapons.

The distinction is important, particularly for security managers, venue operators and anyone responsible for protecting people in publicly accessible locations.

Because while the law recognises the right to defend ourselves and others, it does not provide a general entitlement to prepare, carry or conceal weapons simply because we fear that an attack might happen.

What is instant arming?

Instant arming is a term sometimes used to describe someone taking up an object that is immediately available to defend themselves or another person against an imminent threat.

It might involve an ordinary item that was never designed or positioned as a weapon but becomes relevant because of the immediate circumstances.

Importantly, instant arming is not a separate statutory power or a blanket legal exemption.

The legality of someone's actions depends on established principles of self-defence, defence of others, the relevant weapons legislation and the particular circumstances.

Under English law, a person may use reasonable force to defend themselves or others against an unlawful attack.

The courts recognise that people confronted with violence may have to make decisions quickly, without the opportunity for careful reflection.

However, the force used must still be lawful in the circumstances as the person honestly believed them to be.

There is an important distinction between responding to an immediate threat and preparing in advance to use an object to injure someone if a threat develops in the future.

That distinction was central to my conversation with the venue owner.

The London Bridge attack: a real example of instant arming

One of the clearest real-world examples of an improvised defensive response occurred on 29 November 2019.

During the terrorist attack at Fishmongers' Hall, near London Bridge, Usman Khan attacked attendees at a rehabilitation conference, killing Jack Merritt and Saskia Jones.

As the attack unfolded, members of the public intervened.

Among them was Darryn Frost, who removed a narwhal tusk from a display inside the building and used it to confront the knife-wielding attacker.

Other individuals used objects including a chair and a fire extinguisher.

These were not weapons that had been strategically positioned for use during a terrorist attack.

They were objects already present within the premises that became improvised means of defence in response to an immediate, life-threatening situation.

The distinction is important.

The narwhal tusk had been displayed for a legitimate purpose. It was not being carried by a security officer in anticipation of a possible future attack.

Its use as a defensive object arose because an actual attack was taking place.

That is the type of situation commonly described as instant arming.

It is also important to understand that the incident does not establish an automatic legal exemption. The lawfulness of possessing or using an object must still be considered against the particular circumstances and the principles of self-defence.

Now consider a different scenario.

What if the management of Fishmongers' Hall had deliberately positioned similar objects throughout the premises, with instructions that security personnel should retrieve them to injure an attacker if a terrorist incident occurred?

The objects might have been physically identical.

But the intention behind their placement and possession would have been fundamentally different, raising separate questions under offensive weapons legislation.

The difference is not simply the object. It is the circumstances, intention and immediacy of the threat.

The courage demonstrated by those who intervened at Fishmongers' Hall was extraordinary.

But their actions should not be interpreted as a recommendation that unarmed security personnel routinely confront terrorists.

Nor should the incident be used to justify deliberately creating weapons stores within publicly accessible premises.

Instead, it demonstrates the importance of context when considering actions taken in immediate self-defence.

And it reinforces the point I made to the venue owner who approached me:

There is a significant legal and practical difference between someone improvising a defence when confronted by an attacker and an organisation preparing weapons for a confrontation that may never happen.

What is an offensive weapon under UK law?

The starting point is section 1 of the Prevention of Crime Act 1953, which addresses having an offensive weapon in a public place without lawful authority or reasonable excuse.

The legal definition identifies three broad categories.

1. Weapons made to cause injury

These are articles manufactured for the purpose of causing injury to another person.

Certain types of weapon fall into this category because of their inherent design and purpose.

2. Articles adapted to cause injury

These are ordinary articles that have been physically modified for the purpose of causing injury.

An item may originally have had a legitimate everyday function, but deliberate adaptation can change its legal character.

3. Ordinary articles intended to cause injury

This is perhaps the most important category for security managers to understand.

An object does not necessarily need to have been manufactured or modified as a weapon to become an offensive weapon.

An otherwise ordinary article may fall within the definition when the person possessing it intends to use it to cause injury.

And crucially, that intention can include using it defensively.

The Crown Prosecution Service makes this distinction clear in its guidance on knife and other weapons offences.

An object does not become lawful to carry for protection simply because the person carrying it considers themselves to be acting defensively.

This is where the legal position becomes particularly relevant to the private security industry.

When does an ordinary object become an offensive weapon?

Consider an everyday item kept at a venue for a genuine operational purpose.

Its ordinary presence does not necessarily make it an offensive weapon.

But suppose someone deliberately places that same item behind a reception desk with instructions that it should be used to strike an attacker.

The item's intended purpose has now changed.

The question is no longer simply what the object is.

It becomes why it is there, who has control of it, what it is intended to be used for and whether its possession is lawful.

In a public place, those circumstances may bring the article within the legal definition of an offensive weapon.

There is no requirement that the item must already have been used to injure someone.

Intention can be relevant before any physical confrontation occurs.

Nor does describing an item as emergency equipment automatically change the legal position.

A policy document cannot transform an otherwise unlawful weapons arrangement into a lawful one merely by assigning it a security-related purpose.

The precise circumstances will always matter, including whether the item is genuinely required for legitimate work, where it is kept and whether any statutory defence applies.

But the underlying principle is important.

An ordinary object and an offensive weapon can sometimes be physically identical. What changes is the purpose for which the object is possessed.

Why the timing of the threat matters

There is a significant legal difference between possessing an article because an attack might happen someday and responding to an attack that is actually occurring or immediately anticipated.

The Crown Prosecution Service explains that carrying an offensive weapon in public because of a general or continuing threat does not ordinarily establish a reasonable excuse.

It also recognises that exceptional circumstances may arise where a person anticipates a specific, imminent attack.

This is not permission to carry weapons as a precaution.

The circumstances must be examined individually.

For example, an employee who deliberately keeps an object available for use as a weapon because they are concerned about the general possibility of violence is in a different legal position from someone who instinctively takes hold of an available object while confronted by an immediate unlawful attack.

The latter situation may engage the principles of lawful self-defence.

But the fact that someone is defending themselves does not automatically make every action lawful.

The necessity and reasonableness of the response remain important.

So does the point at which the danger ends.

An action that may be justified during an immediate attack may cease to be justified once the threat has passed.

This is why I would be cautious about anyone presenting instant arming as a straightforward legal entitlement.

It is better understood as a description of a possible defensive response, the legality of which must be assessed against the circumstances.

Can a security officer use an object to defend themselves during a terrorist attack?

Potentially, yes.

Security officers do not lose their ordinary rights of self-defence simply because they are working.

They may be entitled to use reasonable force to protect themselves or another person from an unlawful attack.

That can include circumstances in which an immediately available object is used defensively.

However, a security officer's SIA licence does not give them general authority to carry offensive weapons.

Nor does their employment create a blanket exemption from the law.

The same broad principles of necessity and reasonable force apply.

A further distinction is essential.

The legal ability to defend yourself does not create a professional obligation to confront an armed terrorist.

Security officers are not armed police officers.

Their training, equipment, authority and operational responsibilities are different.

Employers must not develop emergency procedures that assume unarmed security officers will physically confront armed attackers.

Such an expectation could expose employees and others to serious and foreseeable risks.

Protective security arrangements should instead focus on recognising threats, raising the alarm, protecting people, supporting escape or shelter where appropriate and facilitating the emergency services' response.

Physical intervention may become unavoidable in exceptional circumstances.

But it should not be the foundation upon which a venue's counter-terrorism arrangements depend.

Why hiding weapons around a venue is not a sensible protective security strategy

Returning to the venue owner's proposal, there were several reasons why I could not support it.

The first was the legal position.

Deliberately positioning objects for the purpose of injuring a future attacker raises obvious questions under offensive weapons legislation, particularly where those objects are kept in areas accessible to the public or under the control of security personnel.

The fact that the intended target would be a terrorist does not automatically provide lawful authority to possess the weapons.

The second concern was control.

Any object introduced into a venue as a potential weapon creates a risk that it could be accessed, misused or turned against staff or members of the public.

The third concern was the effect on security officers themselves.

If employees are told that weapons have been placed around a venue for their use during an attack, what expectation does that create?

Are they being encouraged to confront an armed attacker?

Have they been trained for that role?

Has the employer assessed the risks associated with that expectation?

And what happens if an officer attempts to retrieve an item when their safest option would have been to escape or take shelter?

There are also potential consequences for insurance, employer liability, health and safety responsibilities and the organisation's wider security arrangements.

Most importantly, I believe the proposal addressed the wrong problem.

The venue owner was understandably concerned about the vulnerability of his staff.

But rather than asking how to equip unarmed security officers to fight an attacker, I encouraged him to consider how the premises could be made safer so that staff and visitors were less likely to find themselves in that position in the first place.

That is a fundamentally different approach.

Designing premises to protect people without creating a weapons capability

Good protective security design should reduce the opportunities available to an attacker and improve the ability of people to respond safely.

This is not necessarily about installing expensive equipment.

It begins with understanding how a building operates, how people move through it and where vulnerabilities exist.

Physical barriers and compartmentation

Doors, walls, access-controlled areas and other physical features can contribute to delaying or restricting an attacker's movement.

The National Protective Security Authority and ProtectUK provide guidance on how existing building features can be used to improve protection against marauding terrorist attacks.

The objective is not to turn ordinary workplaces into fortresses.

It is to understand whether the building provides opportunities to separate people from danger and whether those opportunities can be used effectively.

Safe escape and protected spaces

Premises should be assessed to determine whether people can move away from a threat without inadvertently entering a more dangerous area.

In some circumstances, evacuation may be appropriate.

In others, invacuation or lockdown may offer better protection.

Suitable protected spaces may provide temporary refuge while the situation develops.

These arrangements need to be assessed against the specific risks and physical characteristics of the building.

They must also be compatible with fire safety and emergency escape requirements.

Access control

Controlling access to sensitive areas can reduce vulnerability.

Security managers should consider whether access control arrangements can restrict an attacker's movement without preventing occupants from escaping.

The ability to secure appropriate areas quickly and safely can be more valuable than providing staff with objects intended for physical confrontation.

Communications and alarms

Staff need to know when a threat has been identified and what actions are expected of them.

An effective warning system can help people make appropriate decisions quickly.

Security teams also need reliable ways to communicate with colleagues and emergency services.

An emergency plan that depends on communication systems that do not work throughout the premises is unlikely to be effective.

Training and practical preparation

The best-designed building can still be vulnerable if staff do not understand the protective measures available to them.

Security officers, reception staff, managers, contractors and other relevant personnel should understand their responsibilities.

That includes knowing how to raise an alarm, how to communicate information and what protective actions are available.

It also means recognising the limits of their role.

The objective is to help people make safer decisions, not encourage them to take unnecessary risks.

Martyn's Law: protecting people, not arming security officers

The Terrorism (Protection of Premises) Act 2025, commonly known as Martyn's Law, has increased attention on the responsibilities of those operating qualifying premises and events.

The legislation establishes requirements relating to public protection procedures and, for enhanced-tier premises and qualifying events, appropriate public protection measures.

The four principal response procedures are:

Evacuation
Invacuation
Lockdown
Communication

These measures are intended to improve the ability of organisations to reduce harm during terrorist incidents.

The legislation does not create a general authority for private security officers to carry weapons.

Nor does it require venue operators to establish armed response capabilities.

Indeed, the emphasis on protective procedures reinforces the importance of preparation, communication, appropriate physical measures and effective decision-making.

A venue operator who is concerned about terrorism should be examining how their premises and people can be better protected.

Not assuming that the solution is to provide security officers with concealed weapons.

Seven questions venue operators should ask

If I were advising a venue owner concerned about the vulnerability of unarmed security personnel, I would start with seven questions.

1. Have we assessed the actual threats and vulnerabilities affecting the venue?

Security arrangements should be proportionate to the risks identified, rather than driven entirely by fear of a particular scenario.

2. Can staff recognise and communicate an emerging threat?

Early recognition and effective communication can be critical to reducing harm.

3. Do our premises provide opportunities to move away from danger?

Escape routes, access arrangements and potential protected spaces should be understood and assessed.

4. Can we restrict an attacker's movement without compromising emergency escape?

Existing physical security measures may offer opportunities to delay or separate a threat from potential victims.

5. Do our security officers understand their responsibilities and limitations?

Their role should be clearly defined, realistic and supported by appropriate training.

6. Have we tested our emergency procedures?

A documented lockdown or invacuation procedure is of limited value if staff cannot implement it.

7. Are we inadvertently introducing new risks through our security arrangements?

This is particularly important when considering measures that could create hazards, restrict escape or introduce items intended for use as weapons.

These questions encourage a more structured approach to protective security.

They also move the discussion away from the assumption that the only meaningful response to an armed attacker is to provide staff with something they can fight back with.

Frequently asked questions

Is instant arming legal in the UK?

Instant arming is not a standalone legal defence. Someone who uses an immediately available object to protect themselves or another person may be acting lawfully under established principles of self-defence, depending on the circumstances. The necessity and reasonableness of the force used remain central considerations.

Can an ordinary object become an offensive weapon?

Yes. Under the Prevention of Crime Act 1953, an ordinary article can fall within the definition of an offensive weapon if it is possessed with the intention of causing injury. The article does not necessarily need to have been manufactured or modified as a weapon.

Can security guards carry weapons for self-defence?

An SIA licence does not generally authorise a security officer to carry offensive weapons. Carrying an offensive weapon in a public place because of a general concern about possible violence is not ordinarily a reasonable excuse under the relevant legislation.

Can a venue keep weapons for security staff to use during an attack?

There is no general legal exemption allowing venue operators to establish concealed weapons stores for private security officers. Such an arrangement may raise serious criminal law, health and safety and liability issues. The legality would depend on the precise circumstances and applicable legislation, and specialist legal advice would be essential.

Can a security officer use reasonable force to protect the public?

Yes. Security officers may rely on the ordinary legal principles governing self-defence and defence of others. However, the force used must be lawful in the circumstances, and security officers should not be expected to undertake the role of armed police.

The question we should really be asking

I understood the venue owner's concerns.

He was responsible for a large number of people, employed security officers to protect them and was worried about what might happen if those officers were confronted by a terrorist armed with a knife or another weapon.

His suggestion came from a desire to protect people.

But good intentions do not automatically make a security measure lawful, appropriate or effective.

And I think there is a broader lesson here for our industry.

When discussing the threat of terrorism, it is easy to focus on the attacker and the weapons they might possess.

It is equally easy to conclude that our own personnel are vulnerable because they do not possess comparable equipment.

But protective security should not be measured by our ability to match an attacker's capacity for violence.

It should be measured by how effectively we reduce vulnerability, protect people, create opportunities to escape or shelter and support an appropriate emergency response.

There may be exceptional circumstances in which someone has no realistic alternative but to defend themselves using an immediately available object.

The law recognises that possibility.

But that is very different from deliberately positioning weapons around a venue in anticipation of a future attack.

Instant arming is about responding to an immediate threat. Deliberately providing weapons for a possible future confrontation raises an entirely different set of legal and operational questions.

For me, the answer to the venue owner's concerns was not to hide weapons around his building.

It was to examine how the building, its security arrangements and its people could be better prepared to protect themselves without creating additional risks.

Because the objective of protective security should never be to turn security officers into armed responders.

It should be to reduce the likelihood that anyone has to confront an attacker in the first place.

About the author

Sean Keelan is a former police officer with more than 20 years' experience across policing and the private security industry. He is the founder of Blue Light Security Solutions Ltd, a UK security company providing security services and risk management support.

Sean is a Member of the Security Institute (MSyI), a member of ASIS International and a Freeman of the Worshipful Company of Security Professionals.

His professional interests include counter-terrorism, protective security, emergency preparedness and the protection of publicly accessible locations.