Change Locks When You Move Into a New Property — and What to Fit
When you move into a new property, change the locks. You do not know how many keys are in circulation. Here is what to fit and what British Standard means.
## Change the locks on the day you move in
You have no idea how many copies of the key to your new property exist. The previous owner may have given one to a cleaner, a neighbour, a letting agent, a builder, or a relative. Keys get copied. People forget to return them.
Changing the locks is the first thing to do when you take possession. Not the second day. The first day.
Why outstanding keys are a real risk
The previous owner's locksmith may still hold a key from the last job. Letting agents keep copies as standard. Emergency contacts have spares. After a tenancy ends, keys are supposed to come back — often they do not.
A standard euro cylinder can be copied at any high street key cutter in under 2 minutes. No record is kept. There is no limit on how many copies can be made. If a key existed at any point, it may have been duplicated.
Changing the cylinder does not mean replacing the entire door. On most modern UPVC and composite doors, a new cylinder is a 20-minute job and costs a fraction of what you have just spent on the property.
What locks to fit
Two numbers matter: BS3621 and TS007 3-star.
BS3621 is the British Standard for locks on external doors. A lock with this marking has passed independent tests for strength, pick resistance, drill resistance, and key control. Most home insurance policies in the UK require at least one BS3621-certified lock on each external door. Without it, a burglary claim may be refused.
TS007 3-star is the standard for euro cylinders — the oval lock set into most UPVC and composite doors. A 3-star rating means the cylinder resists both snapping and picking. Cylinder snapping is the most common forced entry method in the UK: a burglar breaks off the exposed section of the cylinder with mole grips, pulls out the rest, and the door opens. A TS007 3-star cylinder stops this.
For most London properties, the right setup is a BS3621 5-lever mortice deadlock fitted to the door frame, plus a TS007 3-star anti-snap cylinder on the UPVC or composite door. If you only have one external door, fit both.
What home insurance actually requires
Check the security conditions section of your policy schedule. The wording varies by insurer but the requirement is usually a British Standard deadlock (BS3621) on each external door, or a multi-point locking system with specific cylinder ratings.
A standard Yale nightlatch does not meet BS3621. It can be opened with a credit card in under 10 seconds. We fit them when customers ask, but we always make that clear. A BS3621-rated deadlock costs around £30 more than a standard one and passes the standard insurers actually require.
The estate agent call
An estate agent called us 20 minutes before a property handover because the previous owner's locksmith had fitted the wrong cylinder — incompatible with the door hardware. We recut and refitted the lock in time. The handover went ahead.
This was not unusual. When locksmiths fit cylinders between tenancies, they sometimes use whatever cylinder is in the van rather than matching the door specification. By the time the next occupant moves in, the lock may not be fitted correctly. A check on possession day takes 5 minutes.
How much it costs in London
Labour for a lock change starts at £109. The cylinder or lock body is quoted separately.
- Standard euro cylinder: £25–£40 - TS007 3-star anti-snap cylinder: £40–£60 - BS3621 5-lever mortice lock: £50–£90
A front door fitted with a new BS3621 deadlock and a TS007 3-star cylinder typically runs £200–£280 all in, parts and labour included. Most jobs are done in a single visit.
When not to change locks yourself
If your door has a UPVC multi-point locking system, do not attempt to replace the cylinder without checking the cam profile first. UPVC doors require specific cam configurations to drive the gearbox. A cylinder with the wrong cam will not engage the mechanism, and a door that will not lock is a bigger problem than an old cylinder.
If the existing cylinder shows signs of forcing or partial snapping, inspect the gearbox before replacing the cylinder alone. A snapped cylinder often damages the cam, meaning the whole mechanism needs replacing — not just the cylinder.
Areas we cover
We carry out lock changes across central London on the same day you call: Westminster, Kensington, Chelsea, Mayfair, Camden, Islington, Shoreditch, the City of London, Southwark, Lambeth, Wandsworth, Hackney, and surrounding areas.