Invacuation, lockdown and the other words nobody explains
Four words, one of which is not really a word. Here is what each one means, when you would use it, and how to tell them apart in the four seconds you would actually have.
Martyn’s Law names four kinds of “public protection procedure”. The names are unhelpful, particularly the second one, which most people have never heard and cannot spell. Strip the language away and they are four answers to one question: something is badly wrong — do we go out, come in, hide, or shout?
1. Evacuation — get everybody out
The one everybody knows, because it looks like a fire drill. But it is not a fire drill, and the difference is the whole point.
In a fire, the building is the danger, so any way out is better than staying in. Here, the danger may be outside one particular door — and if you push 240 people through that door because it is the one you always use, you have walked them into it.
What good looks like
- Five seconds of thought before you shout: where is the problem, and which way is away from it?
- Knowing where each exit actually leads — the front door onto the road, the fire door onto the field, the kitchen door into the alley. Written down once, so nobody has to work it out under pressure.
- A second assembly point, because the first one might be the problem. Most venues have never chosen one. It takes ten seconds and it matters enormously.
- Plain words, said twice, and nobody going back in for a coat.
2. Invacuation — bring everybody in
The word is a coinage — “in” plus “evacuation” — and it means exactly what it sounds like: the safest thing is not to go outside, so you bring people in, away from doors and windows, and shut the building.
It is the procedure people find least intuitive, which is precisely why it needs writing down. Every instinct on a day like that says get out. But if the incident is in the street — a vehicle, an attack, a police instruction to stay put — then sending everybody out of the front door into it makes you the person who made it worse.
The one rule to remember
In. Away from the windows. Doors shut. Stay quiet. Wait for the police.
Two practical things almost nobody thinks about until they have to:
- Glass is the hazard. A blast or a vehicle sends it inward. Get people below the line of the windows and behind something solid. If one wall of your hall is glazed and faces the road, name that wall in your procedure.
- You must say something every few minutes, even when there is nothing new to say. Silence from the person in charge is what turns worry into panic — and people will want to leave, to fetch a car, to “just have a look”. Nobody leaves.
3. Lockdown — someone dangerous is trying to get to us
The hardest one to think about, and the one that takes the fewest seconds to get right.
The national advice comes first and overrides everything: Run. Hide. Tell. If you can get out safely, get out — that always beats hiding. Lockdown is what you do when you cannot get out. Do not let a written procedure talk anybody out of an open door.
What good looks like
- Anyone can call it. There is no time to find the person in charge and ask permission. No code words, either — the volunteer on their first shift is exactly the person who needs to understand, and code words are what they will not remember.
- Lock it if it locks; block it if it does not. Most community buildings have doors that do not lock from the inside. That is not a reason to give up on lockdown — it means barricading is your method, and you should know now what you would push against the door.
- Lights off, phones on silent (silent, not vibrate — vibrate is loud in a quiet room), everyone below the windows, and silence.
- Do not open the door. Not to a knock, not to a familiar voice, not to somebody saying they are the police. The police will not need you to open it. This feels unbearably wrong, and it is right.
4. Communication — the one the other three depend on
Somebody has to raise the alarm. Somebody has to tell 200 people what to do. Somebody has to ring 999 and stay on the line. If those three jobs are not named before anything happens, they get done late, twice, or not at all.
The most common failure in a real incident is not panic. It is fifty people each assuming one of the other forty-nine had already called. Two calls waste nobody’s time. Nought calls is a catastrophe.
| Job | What they do |
|---|---|
| The Voice | Makes the announcement. Says the words. Says them twice. |
| The Caller | Rings 999 and stays on the line. Does nothing else — they do not also help with the doors. |
| The Sweeper | Checks the toilets, the kitchen, the store cupboard, upstairs. Reports back. |
Three names on a whiteboard, ten minutes before the doors open. That is the difference between a procedure that exists on paper and a procedure that happens.
Telling them apart when it matters
| If the danger is… | You probably… |
|---|---|
| Inside the building, and you can get out | Evacuate — away from where the problem is |
| Outside, in the street or the car park | Invacuate — in, away from the glass, doors shut |
| Coming towards you and you cannot get out | Lock down — lock, block, get low, be quiet |
| Any of the above | Communicate — say it plainly, ring 999, do not assume someone else has |
And the rule that sits above all four: these procedures serve your judgement, they do not replace it. If the situation changes — a fire starts during an invacuation — you change with it. Keeping people inside a burning building because a document said “invacuate” would be a catastrophe, and no procedure worth having would ask you to.
Free training that is genuinely worth the hour
ProtectUK — run by Counter Terrorism Policing — publishes free guidance and free e-learning, including ACT Awareness. It costs nothing, it is not a sales funnel, and it is the best hour a volunteer committee could spend on this. We would rather you did that than bought anything from us.
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Common questions
What does invacuation mean?
Bringing people into the building and away from doors and windows, and shutting it, because the danger is outside and going out would be worse. It is the opposite of evacuation, and it is the procedure people find least intuitive — which is exactly why it is worth agreeing in advance.
What is the difference between lockdown and invacuation?
Invacuation is a response to danger outside: come in, away from the glass, shut the doors, stay calm and wait. Lockdown is a response to someone dangerous trying to reach you: lock or barricade a room, lights off, get low, stay silent, and do not open the door.
Is evacuation just our fire drill?
The route is often the same, but the reason is not. In a fire the building is the danger, so any exit will do. Under Martyn’s Law the danger may be immediately outside one particular exit — so the first decision is which way is away from the problem, and that may not be the door you always use.
Do we have to practise these?
The standard tier does not mandate drills. But talking your volunteers through the four procedures for ten minutes before a big event — and naming who announces, who calls 999 and who sweeps the building — costs nothing and is what turns a written plan into something that would actually happen.
Where this comes from
Everything above is our plain-English reading of the following. Where we quote a paragraph number, it is from the Home Office statutory guidance. If you want the law itself rather than our summary of it, start with the first link.
- Terrorism (Protection of Premises) Act 2025 (c. 10) legislation.gov.uk The Act itself. Royal Assent 3 April 2025.
- Terrorism (Protection of Premises) Act 2025: statutory guidance GOV.UK (Home Office) Published April 2026, last updated 18 May 2026. The paragraph numbers quoted in these guides are from this document.
- ProtectUK Counter Terrorism Policing Free guidance and free e-learning (ACT Awareness). The training is genuinely good and costs nothing.
Last reviewed . Martyn’s Law is not yet in force and the guidance is still developing — if you are reading this long after that date, check the sources above for anything newer.
This is guidance, not a legal determination. Standfast helps you think clearly and get ready. It does not decide your legal position, and nothing on this page is legal advice. If your circumstances are unusual, or a great deal turns on the answer, take advice.