The removal van has gone, the kettle is somewhere in box 14, and you’ve just been handed two keys on a fob. Here’s the question almost nobody asks on moving day: how many other keys to this door are still out there?
The honest answer is that you don’t know, and neither did the seller. By the end of this guide you’ll know exactly who might still be able to walk in, what your insurer quietly expects from you, and how to sort it in one visit without overpaying.
The short answer
Yes. Change the cylinders or locks on every external door in your first week. It usually takes under an hour, costs far less than most people expect, and it’s the only way to be sure nobody else holds a working key. If you rent, ask your landlord first and keep it in writing.
Who could still have a key to your new home
Keys travel further than people think. A three-bedroom house that has changed hands twice could easily have a dozen copies floating around, and the seller is very unlikely to have collected them all back.
- The previous owners, plus any family members or friends they gave a spare to.
- Past tenants, if the property was ever rented out, and their partners or flatmates.
- Cleaners, dog walkers, childminders and builders who were trusted with a key over the years.
- Estate and letting agents, who often hold sets for viewings.
- Neighbours who kept a spare “just in case”.
- On new builds: site managers, subcontractors and snagging teams who used master or construction keys.
This isn’t a theoretical worry. Research by Yale, quoted by the Master Locksmiths Association, found that 32% of people still have a key to a previous home. Nearly a third of everyone who has ever moved could, in theory, let themselves back in somewhere.
Your insurer cares more than you think
Most home insurance policies pay out on theft only when there’s evidence of forced or violent entry. If a burglar opens your front door with an old key, there’s no damage to show, and that’s exactly the situation where claims get questioned or refused.
Policies also tend to name the locks they expect on external doors. On older wooden doors that usually means a five-lever mortice deadlock to BS3621. On uPVC and composite doors it usually means an anti-snap euro cylinder rated TS007 3-star or Sold Secure SS312 Diamond. If the locks you inherited don’t meet the wording in your policy, you could be underinsured from day one without knowing it.
What to change, door by door
You rarely need to replace the whole lock. On most London homes the job comes down to swapping cylinders, which is quick and clean. Here’s how it usually breaks down.
| Door | What usually gets changed | Typical London price (daytime) |
|---|---|---|
| uPVC or composite front door | Euro cylinder only, upgraded to TS007 3-star anti-snap | £90 to £120 |
| Wooden front door | BS3621 mortice deadlock, plus night latch cylinder if fitted | £110 to £160 per lock |
| Back or side door | Same as above, depending on door type | £90 to £160 |
| French or patio doors | Euro cylinder | £90 to £120 |
| Garage and outbuildings | Padlocks or rim locks, often DIY | From £20 for parts |
Doing several doors in one visit is where you save. You pay for one call-out instead of three, and a locksmith can key every cylinder alike so a single key opens the front, back and patio doors. For a typical terraced house with a uPVC front and back door, that usually lands somewhere around £180 to £240 in total. Our guide prices show the full list.
Can I just do it myself?
Swapping a euro cylinder is within reach if you’re handy. You measure the cylinder, buy the right size, undo one retaining screw and slide it out. The catch is the measuring. Get the length wrong by a few millimetres and the cylinder sticks out, which makes it easier to snap and can breach your policy. Mortice locks are a different story: cutting and fitting a new one into a wooden door is a job for someone who does it every day.
A first-week security checklist
Locks are the big one, but they aren’t the only thing the previous owners leave behind. Work through this while you unpack.
- ☐ Change cylinders or locks on every external door, including back and patio doors.
- ☐ Check window locks work and that you have the keys for them.
- ☐ Reset the burglar alarm code, or ask an engineer to do it.
- ☐ Change the garage door code, gate code and any smart lock or doorbell accounts.
- ☐ Remove the seller’s access from any smart home apps and Wi-Fi.
- ☐ Count your new keys and write down who you give copies to.
- ☐ Read your insurance policy’s security section and keep the locksmith’s invoice as proof.
Renting? The rules are different
Tenants and landlords sit on opposite sides of this question, so it’s worth taking each in turn.
If you’re a tenant
Most tenancy agreements say you need the landlord’s written permission before changing the locks, and many require you to hand over a copy of the new key. Ask first, explain why, and keep the reply. Plenty of landlords are happy for you to arrange it, sometimes at their cost. If you change locks without permission, you may be asked to pay to put the originals back when you leave.
If you’re a landlord or letting agent
Changing locks between tenancies isn’t a legal requirement in England, but it’s the simplest way to show you’ve taken reasonable care of the property and your new tenant’s safety. Previous tenants rarely return every copy. A cylinder swap at check-out costs less than a single weekend void, and it removes a very awkward conversation if something goes missing later. We can keep a record of the keys issued for each property and invoice the agent directly.
Questions people ask after moving in
How soon should I change the locks?
Ideally within the first few days, and before you move valuables in if you can. Many people book the locksmith for the afternoon they collect the keys.
Is a new build safe without changing locks?
Not necessarily. New builds are often fitted with construction keys used by the site team, and builders sometimes fit basic cylinders to keep costs down. Check the cylinder for a TS007 3-star or SS312 Diamond mark. If there isn’t one, it’s worth upgrading.
Can I just rekey instead of replacing?
Most UK homes use euro cylinders, which are cheaper to replace than to rekey. Rekeying makes more sense for some high-security systems where the cylinder itself is expensive.
Do I need to change the locks if the seller gave me all the keys?
You can’t know that you have all of them, and the seller can’t either. Copies get cut without anyone keeping track, which is exactly why insurers and the MLA both recommend changing them.
Will new locks lower my insurance premium?
Sometimes. Some insurers offer discounts for high-security locks, and the right locks make sure you meet the policy’s minimum standard in the first place. Ask your insurer when you renew.