How do I know if my lock is BS3621?

Look on the edge of the door for the lock's faceplate. A genuine BS3621 lock carries a heart-shaped British Standard kitemark and the number stamped on it. No mark usually means it isn't rated.

Does every door need a BS3621 lock?

Insurers focus on external and final exit doors. Internal doors don't need it. We can tell you exactly which of your doors should be upgraded.

Is upgrading expensive?

It's typically a quick, affordable job — often just the final exit door and back door. Getting it right can also keep your insurance valid, so it tends to pay for itself.

BS3621 explained: the lock standard your insurer actually wants

That string of numbers on your insurance paperwork has a real meaning — and getting it wrong can affect a claim. Here's the plain-English version.

Dig into your home insurance and you'll usually find a line about "BS3621" locks on external doors. It sounds like jargon, but it's worth understanding — because if your locks don't meet it, a claim after a break-in can get complicated.

What BS3621 actually is

BS3621 is the British Standard for a thief-resistant lock that's key-operated from both sides. In practice it covers five-lever mortice deadlocks and certain euro cylinders and nightlatches that have been independently tested to resist drilling, picking and forcing. A genuine one carries a small British Standard kitemark — a heart-shaped stamp — on the faceplate or body.

How to check your own locks

Open the door and look at the edge of the lock (the faceplate) for the kitemark and "BS3621".
On a mortice lock, count the levers if it's printed — five-lever is the one insurers want, three-lever isn't enough for a final exit door.
On a euro cylinder, look for a marked anti-snap / British Standard cylinder; older plain cylinders usually aren't rated.
No markings? It's likely not BS-rated — worth getting checked.

Why it matters for a claim

Many policies make BS-standard locks a condition of cover. If you're burgled through a door that didn't meet the standard your policy specified, the insurer can question or reduce the payout. Getting the right locks fitted isn't just about security — it protects the cover you're already paying for.

Getting it sorted

It's usually a straightforward upgrade — fitting a five-lever mortice or a British Standard anti-snap cylinder to the doors that need it. If you're not sure what you've got, a quick look will tell you, and a short visit puts it right.

A security survey checks every door against what your insurer expects, or we can simply upgrade the locks that fall short.

Security survey

Need a hand with this?

Two Keys is a father-and-son locksmith team in Egham — UKLA Trusted & Vetted, DBS-checked, fully insured. Straight prices, agreed before we set off.

We cover Egham · Staines-upon-Thames · Windsor · Caterham and the wider Surrey, west London and east Berkshire area — see full coverage.

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