Just moved in? Whether to change the locks, and what your insurer expects

You have the keys. Two sets, maybe three.

The uncomfortable question nobody asks the estate agent: how many other sets are there? The previous owners. Their grown-up children. A cleaner. A dog walker. The builder who did the extension in 2019. A previous tenant who never handed theirs back.

Nobody knows. That is the honest answer, and it is why this is worth twenty minutes of your first week.

If you have bought the property

Change the locks. It is a small job and it removes an unknown.

You are not being paranoid. Conveyancing does not audit keys, sellers genuinely forget who has one, and there is no register anywhere. The unknown is real and it is permanent until you deal with it.

The good news is that it is usually cheap — see below.

If you are renting

Ask first, in writing.

Most tenancy agreements either forbid changing the locks or require you to give the landlord a key. Changing a lock and not restoring it at the end of the tenancy is a routine deposit deduction.

But you can absolutely ask, and a reasonable landlord usually agrees — especially if you give a reason. Good reasons include a previous tenant who did not return keys, a break-in in the area, or a personal safety concern.

If it is a safety concern, say so plainly. An ex-partner with keys, someone you have left, or anyone you have reason to fear is a serious matter and most landlords act quickly. If you are dealing with domestic abuse, the National Domestic Abuse Helpline is 0808 2000 247, free and 24 hours, and can advise on this specifically.

Keep the reply in writing either way.

The bit that costs different money

This is where people overpay, and it is a genuinely simple distinction.

If you have a uPVC or composite door: you probably only need a new cylinder

The euro cylinder is the flat, figure-of-eight barrel the key goes into. It is a separate component from the mechanism that runs up the edge of the door.

Swapping just the cylinder gives you a completely new key. The whole rest of the door is untouched. It is a small job, and anyone quoting you for a full mechanism replacement to achieve a key change should be asked to explain why.

Insist on the rating while you are doing it. Since you are paying for a new cylinder anyway, pay slightly more for one rated TS007 3-star or Sold Secure Diamond — a cheap unrated cylinder is vulnerable to snapping. Full detail in anti-snap locks explained.

If you have a wooden door: check the standard before you buy

Wooden front doors usually have a mortice deadlock buried in the edge.

The one to look for is BS 3621, and it matters beyond security: many home insurance policies require a BS 3621 rated deadlock on final exit doors.

So before anyone fits anything:

1. Read your own policy wording. Not what a locksmith says it says — the actual document. It takes two minutes and it is the only version that counts at claim time.
2. Look at the existing lock. The Kitemark and the BS 3621 number are stamped on the faceplate on the edge of the door.
3. If it is not rated and your policy requires it, fix that now, not after a claim is refused.

The rest of the first-week list

While you are thinking about it:

• Every external door, not just the front. Back doors and side gates are the ones people forget, and they are the ones burglars do not.
• Window locks, and whether the keys for them exist at all.
• The garage or shed. Often the weakest lock on the property, and often where the ladder lives.
• Any key safe left on the wall. Change the code, or remove it. You have no idea who knows the old one.
• Smart locks and app access. If there is a smart lock, a video doorbell or a keypad, factory-reset it and remove every previous account. A previous owner still holding app access is a modern version of the same problem.

Getting it done without being overcharged

This is a booked daytime job, never an emergency one. That alone halves the price. Then:

• Get the total in writing before anyone travels — callout, labour, parts, VAT.
• Verify the locksmith on the Master Locksmiths Association directory, on the MLA’s own site rather than from a logo on theirs. Locksmithing is not a licensed trade in the UK, so this is the closest thing to a check that exists.
• Ask for the rating in writing on the invoice — “TS007 3-star” or “Sold Secure Diamond”, not “new cylinder”.
• Keep the packaging, so you can prove what went into your door.

The full method is in how to check a locksmith is genuine, and you can check any figure you are quoted against the price ranges.

And the thing everyone forgets

Cut a spare and leave it with someone reachable.

Not under the mat, not in a plant pot, not in a key safe with the default code. With an actual person — a neighbour, a friend, a family member in the next borough.

You have just paid to control who holds a key to your home. Spend another five pounds making sure one of them is somewhere you can get to it at 2am.