British Standard Locks — BS3621 Supply and Fitting
British Standard BS3621 is the UK’s primary standard for residential security locks. If your home insurance policy mentions “British Standard locks” — and most do — it is referring to this standard. Fitting locks that meet BS3621 is not merely about reducing burglary risk; it is a contractual condition of most UK home insurance policies. A claim made after a break-in where the locks did not meet BS3621 may be denied. Our engineers supply and fit the full range of BS3621-compliant locks, from mortice deadlocks to high-security euro cylinders.
What Does BS3621 Mean?
British Standard BS3621 specifies the minimum security requirements for locks fitted to external doors in UK residential and commercial properties. The standard covers:
- Key security — The lock must have a minimum of 1,000 key differs (combinations), making key duplication without the manufacturer’s authority extremely difficult
- Bolt security — The deadbolt must be hardened steel, bolt-through construction, and resistant to sawing and cutting
- Anti-pick — The mechanism must resist pick tools for a minimum time period tested by the British Standards Institution
- Anti-drill — The cylinder or case must include hardened steel inserts that defeat drill attacks
- Five levers minimum — Mortice locks must have at least five levers (the spring-loaded mechanism elements that the key operates)
Locks that pass BS3621 testing carry the BSI Kitemark — a small diamond-shaped logo with “BSI” inside. Always look for this mark when purchasing security locks. Our engineers carry only Kitemark-certified locks.
Types of British Standard Lock We Fit
Five-lever mortice deadlock (BS3621) is the standard security lock for timber front and back doors. It is fitted into a pocket cut into the door edge, with a keyhole on the face. We stock Union, Chubb, and ERA mortice deadlocks in the full range of case sizes to fit UK door thicknesses from 35mm to 54mm. Where a door has a single Yale-type latch as its only lock, adding a mortice deadlock is usually necessary to meet insurer requirements.
British Standard deadlocking nightlatch — A surface-mounted rim lock (Yale-type) can also meet BS3621 if it is a deadlocking model — one where the latch deadlocks when the door is closed, preventing it from being retracted by manipulation. Yale Superior, Banham, and Ingersoll all produce BS3621 rim locks. These are appropriate for properties where a mortice lock cannot be fitted due to door construction.
Euro cylinder upgrades — Euro cylinders themselves are not covered by BS3621 (which predates their widespread use), but modern insurance requirements increasingly specify anti-snap cylinders. The Sold Secure Diamond and TS007 3-star standards cover euro cylinders. We fit Ultion, Yale Platinum, Mul-T-Lock, and ERA Fortress cylinders — all independently tested to the highest UK security standards.
British Standard padlocks — For outbuildings, garages, and gates, we supply and fit padlocks to BS EN 12320 (the European equivalent standard for padlocks), including closed-shackle models that resist cropping and levering.
Insurance Compliance Confirmation
After fitting British Standard locks, we can provide a written confirmation of the locks installed, including the BS standard number and Kitemark reference. This document satisfies most insurers when reviewing security compliance after a claim. We recommend requesting this at every lock change.
Do I Need to Change All My Locks?
Not necessarily. Most insurance policies require BS3621 locks on all external doors — front, back, and any side access doors. Internal doors between your property and a shared space (such as a flat door or a door to a garage) may also be subject to requirements. Our engineer will assess all external access points and advise on which, if any, locks need upgrading. We never recommend unnecessary work.
British Standard Locks for Landlords
Landlords have a particular obligation to ensure that their properties are secured to a standard that does not invalidate their insurance. Many landlord insurance policies specify BS3621 locks on all external doors and may also require mortice deadlocks on communal entrance doors in multi-occupancy buildings. We work with landlords and letting agents across our coverage areas and can supply written documentation confirming compliance for each property.
Pricing
British Standard five-lever mortice deadlock supply and fitting starts from £120 including a quality lock and two keys. British Standard deadlocking nightlatch from £99. Anti-snap euro cylinder upgrades from £79. All prices given upfront; no call-out fee. Call 0330 341 4041 to book.
