Upgrading to British Standard locks for better protection

Why the night shift matters most for your front door

Most of us lock up on autopilot. The latch clicks, the bolt turns, and we head upstairs without giving the lock another thought. But between about eleven at night and six in the morning, that lock is doing its most important work of the day — while you are asleep, with no chance of hearing a quiet attempt at the door. If it is an old two- or three-lever mortice lock, or a rim latch with a spring bolt that can be slipped with a piece of plastic, it may be offering far less protection than you assume.

Upgrading to a lock that meets British Standard BS 3621 is one of the most straightforward improvements you can make to a home's security — and in many cases it is something your insurer already expects.

What BS 3621 actually means

BS 3621 is the British Standard for thief-resistant locks. To carry it, a lock must pass independent testing against the attacks a burglar would actually use: picking, drilling, sawing and brute force. Certified locks usually carry the Kitemark, and the standard number should appear on the packaging or the lock itself.

In practice, most BS 3621 locks are five-lever mortice deadlocks. "Mortice" simply means the lock body sits in a pocket cut inside the door rather than being screwed to the surface. Look for:

• Five levers rather than two or three. Levers are the internal wards that make a lock hard to pick, and the difference in resistance is significant.
• A substantial deadbolt throw. Aim for at least 20mm of bolt engagement into the frame.
• Drill and pick resistance. Hardened plates and rollers should protect the critical parts of the mechanism.
• Plenty of key differs. This stops a key from one lock being adapted to open another.
• The Kitemark and standard number. If it is not marked, treat the claim with caution.

Some sashlocks, which combine a latch with a deadbolt, also meet the standard, so you are not limited to one design. What matters is the certification, not the shape of the furniture.

Key egress, fire safety and the alternatives

One point is often missed. A BS 3621 lock is operated by a key from both sides, so you need a key to get out as well as in — and in a fire, that can cost precious seconds. Newer standards cover keyless egress: BS 8621 for locks with a thumb turn inside and a key outside, and BS 10621 for dual-mode locks. If anyone in the household is young, elderly, or might struggle to find a key in smoke, ask your locksmith about these, and check that your insurer accepts them.

If you do keep a key-operated lock, leave the key on a hook close to the door but out of sight of windows and beyond the reach of the letterbox — and make sure everyone in the house knows where it lives.

Fitting matters as much as the lock

A good lock badly fitted is worth less than a modest lock fitted well. A mortice lock is only as strong as the timber around it, and the keep — the plate the bolt slides into on the frame — is often the weakest point. A competent fitter will check:

• The door itself. A hollow or flimsy door will not hold a mortice lock; you want solid timber around 44mm thick.
• The frame and lining. The keep should be fixed with long screws that reach the structural frame, not just the thin lining.
• Flush fitting. Anything protruding can be gripped and snapped, so euro cylinders should not stand more than about 3mm proud of the door.
• Positioning. Height and depth both affect how much leverage an intruder can apply.

Cutting a mortice pocket is not a job to learn on your own front door. Use a qualified, insured locksmith who belongs to a recognised trade association, and ask for a certificate or itemised invoice showing the standard of the lock supplied.

Tick the insurance box

Many home policies include a security condition requiring external final exit doors to be fitted with a lock to BS 3621 or an equivalent standard, and some name a five-lever mortice deadlock specifically. It is usually buried in the small print rather than the summary, so read the wording. If you upgrade, tell your insurer, photograph the fitted lock and its Kitemark, and file the receipt with your policy documents. It could save an argument if you ever need to claim.

A simple night-time routine

The lock is the foundation, but a few habits around it make the whole thing work better:

• Turn the mortice lock as well as the latch before bed — a spring latch alone is not security.
• Keep car keys well away from the front door and letterbox, and use a signal-blocking pouch if your car is keyless.
• Fit a letterbox guard, and never leave keys or a handbag on a hall table in view of the glass.
• Use timer plugs or dusk-to-dawn sensor lights at the front and rear; a light coming on is a strong deterrent.
• Check ground-floor windows and patio doors before you turn in, and set any alarm to its night or stay mode.
• Never hide a spare key outside. Give one to a trusted neighbour instead.

None of this is expensive, and most of it takes a minute. Get the lock right, have it fitted properly, and you can sleep a good deal more soundly.