Lawbite: Clarifying Martyn’s Law: what is the principal use?

Regulations have now come into force offering clarity on a key aspect of the Terrorism (Protection of Premises) Act 2025 (the “Act”), more commonly known as Martyn’s Law.

The Terrorism (Protection of Premises) (Principal Use of Premises) Regulations 2026 (SI 2026/1005) (the “Regulations”) came into force on 15 October 2026, and clarify the principal use of mixed-use buildings as it relates to the Act.

Owners and occupiers of retail, leisure, hospitality, health and education premises (amongst other premises with Schedule 1 uses) should take particular note: getting the principal use wrong could mean premises are wrongly treated as in or out of scope, or the wrong person is treated as responsible for non-compliance with the Act.

The Act, which received Royal Assent on 3 April 2025, imposes counter-terrorism preparedness duties on qualifying premises and events. These duties are not yet in force, but they are expected to take effect around April 2027, subject to commencement regulations. In the meantime, the Home Office is encouraging those who fall within the scope of the Act to begin considering the requirements early.

This development will be most relevant to landlords, tenants, managing agents, investors and lenders.

What’s the purpose of the Act?

The Act is intended to improve public protection from terrorism by requiring certain publicly accessible premises and events to be prepared to respond to an attack. It is commonly known as "Martyn’s Law", in tribute to Martyn Hett, one of the 22 people killed in the Manchester Arena attack.

What does the Act require?

The Act requires those responsible for qualifying premises and events to take steps to prepare for potential terrorist attacks.

It creates two tiers: 

• standard tier premises (where 200 to 799 people may reasonably be expected to be present at the same time), which must notify the regulator and have appropriate public protection procedures (such as evacuation, invacuation, lockdown and communication), so far as reasonably practicable; and
• enhanced tier premises and qualifying events (800 or more people), which must also put in place public protection measures so far as reasonably practicable, document their approach and designate a senior individual. 

Certain premises, such as places of worship and some education and childcare premises, remain in the standard tier even where 800 or more people may be present.

The Security Industry Authority is the regulator and can issue compliance and restriction notices and impose financial penalties of up to £18 million or 5% of worldwide revenue (whichever is greater) for enhanced tier failures, and up to £10,000 for standard tier failures, together with daily penalties for continuing breaches. Certain breaches are also criminal offences.

To be “qualifying premises”, premises must: 

• consist of a building (or a building and land);
• be wholly or mainly used for one or more uses specified in Schedule 1 to the Act;
• be such that it is reasonable to expect at least 200 people to be present at the same time from time to time; and
• not be excluded under Schedule 2 to the Act.

Offices and residential uses are not Schedule 1 uses, so a building used wholly or mainly for those purposes may fall outside scope altogether.

The person responsible for qualifying premises is the person who has control of them in connection with their relevant Schedule 1 use - for example, a landlord or agent controlling a shopping centre’s common parts. Where more than one person has control, each may be responsible, and the Act imposes duties to co-operate, so lease structures and management arrangements will matter.

What do the Regulations say?

As you would expect, many buildings host several Schedule 1 uses at once. Where that is the case, the principal use determines which use is relevant. As the Act does not define “principal use”, it allows the Secretary of State to prescribe factors for determining it.

The Regulations and the associated statutory guidance now set out how to identify the principal use where there are multiple relevant uses.

Determining the principal use

The principal use is the use that most closely reflects the purpose and nature of the premises, taking into account relevant factors including:

• whether the premises were built or adapted for a particular Schedule 1 use;
• whether that use continues; 
• the premises’ physical characteristics; and
• any relevant local authority classification.

If those factors do not identify a principal use, wider relevant circumstances may also be considered, including:

• whether each use occupies all or part of the premises;
• the proportion occupied by each use;
• how long each use occupies the premises during any relevant period; and
• whether one use supports another.

What should you do

For those with potentially qualifying premises in their control:

• review your portfolio and flag premises where 200 or more people may reasonably be expected to be present at the same time, noting which tier applies;
• apply the principal use test to every mixed-use building and record your reasoning, as it may need to be justified to the regulator;
• consider who has control of each part of a building, as landlords, tenants, managing agents, receivers and mortgagees in possession could each be responsible and, depending on the degree of control, may need to co-operate;
• check alteration, compliance-with-statute and service charge provisions, as there will be questions over who can carry out and who pays for compliance works and measures;
• speak to insurers early about terrorism and public liability cover; and
• factor compliance with the Act into due diligence, new leases and financing, as non-compliance may affect value and lettability.