A working locksmith's pick of the locks that actually stop burglars — BS3621 mortice deadlocks, TS007 3-star anti-snap cylinders, and the smart locks worth fitting. No marketing fluff, just what survives real attacks and keeps your insurer happy.
A full walkthrough of the standards, the brands, the attacks they resist and what your insurer expects. Skip to any section below.
More than 500 UK homes are burgled every day, and the overwhelming majority of forced entries come through the front or back door. The weakest point in most of those doors isn't the wood, the glass or the frame — it's the lock sitting inside it.
This guide is written from the van, not a catalogue. It's the exact advice our engineers give South London customers every week when we're asked "what should I actually fit?" — whether that's after a lockout, a worrying insurance renewal, or a break-in on their road. The locks that survive real attacks are the same handful of proven mechanical and hybrid designs. They haven't changed dramatically in a decade. Marketing has.
We'll cover the three UK standards that actually matter — BS3621, TS007 and Sold Secure — what they mean in plain English, which brands get certified (Union, Chubb, ERA, Yale Platinum, Avocet ABS, Brisant Ultion), and how to match the right lock to your door material. If you're comparing options, our Locksmith Advice hub has the companion guides, and our Lock Types library covers each mechanism in depth.
Not sure what you've got on your door? Send a photo of the edge of your door and the existing lock to our team via Contact Us — we'll identify the brand, the standard (if any), and the right upgrade. Locksmith South London engineers cover every postcode listed on our Areas We Cover page, and we've been fitting these exact locks since 2015.
Ignore the word "secure" on the packaging. These three certification marks are the only ones that matter in a UK insurance claim or a real forced-entry test.
British Standard 3621 — Thief-resistant locks
The backbone standard for wooden front and back doors. Requires a minimum 5 levers, a hardened bolt that extends 20mm+, and proven resistance to 10+ minutes of manual attack.
Technical Specification 007 — Kitemark for cylinders
The anti-snap standard, introduced after lock snapping became the UK's dominant burglary method. Stars are awarded to both the cylinder and the door furniture around it.
Bronze \u2192 Silver \u2192 Gold \u2192 Diamond
An independent UK testing house (part of the Master Locksmiths Association) that attacks locks with real burglary tools. A Diamond-rated cylinder is effectively equivalent to TS007 3-star.
The right lock for a Victorian timber door is the wrong lock for a modern uPVC door. Here's the short version every UK homeowner needs — use it as a checklist before you spend a pound.
Victorian, Edwardian, solid hardwood
Most modern back, side & patio doors
GRP skin, foam core (post-2010)
Modern glazed, bi-fold, steel-core
Ranked by certification, real-world attack resistance and how often we fit them in South London. Prices below are supply-and-fit by our engineers.
The cylinder that redefined UK anti-snap. A hidden second lock activates the moment someone tries to snap the cam, and the £1,000 guarantee backs it against insurance disputes. The default fit on composite doors in South London.
Hardened molybdenum alloy body, sidebar picking defence, anti-bump slider system. Secured by Design approved and a favourite of UK police crime prevention officers. Genuinely excellent value.
The workhorse BS3621 mortice deadlock on British timber front doors since the 1970s. Cases machined from solid steel, 20mm+ bolt throw, and a keyway that's genuinely hard to pick. Insurance-company default.
The best-known name on a certified body — hardened central bar, 16 anti-pick pins, and compatibility with Yale Linus smart module if you want a hybrid setup later. Trusted by UK housebuilders.
The only UK smart lock we recommend without caveats — because the actual security comes from the Ultion 3-star cylinder underneath, not the electronics. Remote unlock, auto-lock and guest PINs without compromising the mechanical bite.
If your front door is solid wood, nothing beats a BS3621 5-lever mortice deadlock. It sits inside a pocket cut into the door edge, so there's nothing protruding to lever, kick or snap. The bolt itself is a slab of hardened steel that throws 20mm+ into a reinforced keep, and the lever-pack behind it is genuinely difficult to pick.
Insurance matters here. Almost every UK home policy lists BS3621 as a requirement for "final exit doors" — the front door, any back door, and the door off an attached garage. Without it, a claim can be argued or refused. BS3621 compliance is the single easiest box to tick.
A sashlock combines a bolt with a latch and handles — fit it on a back door that needs to open without a key during the day. A deadlock throws a bolt only, operated by key from both sides — fit it on a front door where you want absolute deadlock on exit. For full UK insurance compliance, the deadlock version is the safer default.
Our pick for timber front doors: Union 2134E or Chubb 3G114 — both BS3621 Kitemarked, both fit the standard 67mm UK mortice pocket, both come with spare keys as standard. If you want longer-term convenience, ask for keyed-alike fitting so front door, back door and garage side door all run one key.
Open your uPVC door, drop the handle, and look at the edge. If you can see a brass or steel oval sticking out past the handle plate, you have a euro cylinder lock. And if that cylinder sticks out more than 3mm, or doesn't carry a Kitemark, it's the single weakest point in your house.
A standard 1-star euro cylinder can be snapped with a builder's hammer, a pair of mole grips and thirty seconds of nerve. The attacker bends the cylinder until the cam breaks, then reaches in and retracts the whole multi-point lock from inside. Lock snapping became so common the UK government introduced TS007 specifically to stop it.
1★
Basic protection
2★★
Handle / escutcheon only
3★★★
Cylinder alone passes
The simple rule: a 3-star cylinder on its own meets the standard. Or, fit a 1-star cylinder with a 2-star handle over it and you reach the same protection tier. Most insurers accept either configuration.
Measure first. Euro cylinders come in lengths from 60mm to 120mm and the sizes are not standard between brands. Fitting a cylinder that's even 5mm too long creates a snap point. If you're unsure, send us a photo of your existing lock — we carry the common UK sizes on the van.
When you lift the handle on a uPVC or composite door, a strip inside the door edge fires hooks, rollers and a shootbolt into the frame all at once. That's a multi-point locking system — and it's excellent, until something in the strip wears out.
The security of that whole system still depends on the small euro cylinder we covered above. Replace a 1-star cylinder with a 3-star anti-snap version and every one of those locking points becomes effectively un-bypassable from outside. But the gearbox itself also matters, and it's the part most UK homeowners forget about.
If you have any of these symptoms, a uPVC door lock repair is usually cheaper than a full replacement — we carry the six common UK gearbox brands (Fuhr, Yale, Mila, Winkhaus, GU, Roto) on the van. Pair a new gearbox with a 3-star cylinder upgrade at the same visit and you get a 15-year security solution for under £400 on most doors.
The only question that matters with a smart lock is: what's the mechanical lock underneath? Pair the right core with the right module and you get genuine convenience without losing security.
A Brisant Ultion 3-star cylinder with a Nuki smart module retrofitted on the inside — nothing changes on the outside of the door. Full explanation on our Smart Door Locks page.
Three standards, three different products, one simple way to compare them. If you only read one table on this page, make it this one.
| Rating | Best for | Attack resistance | Insurer accepted |
|---|---|---|---|
| BS3621 Mortice | Timber front & back doors | 10+ min manual attack, drill, pick & saw protection | Yes — industry standard |
| TS007 1★ Cylinder | Internal or low-risk doors | Basic protection only — will snap under attack | Only with a 2-star handle |
| TS007 3★ Cylinder | uPVC, composite, aluminium external doors | Snap, drill, pick, bump — all tested | Yes — standalone |
| Sold Secure Gold | Mid-tier cylinder, padlock, chain | Dedicated tools — moderate resistance | Varies — check your policy |
| Sold Secure Diamond | Top-tier cylinder, high-risk doors | Specialist tools — highest mechanical rating available | Yes — equivalent to TS007 3★ |
| Secured by Design | UK Police police-preferred overlay badge | Only applied to products that already meet TS007 or BS3621 | Yes — bonus signal |
Designing your security around the real techniques used in UK break-ins — not the ones you see in films. Every one of these is defeated by the lock choices above.
27%
of UK door burglaries
Mole grips, a builder's hammer and brute force. Bends the cylinder until the cam breaks, then the door opens from inside. Takes 10–15 seconds on a cheap cylinder.
17%
of forced entries
Cordless drill targets the pin-chamber line or the bolt itself. Defeats older mortice cases and unrated euro cylinders in under 60 seconds.
9%
of burglaries
A specially cut "bump key" hit with a rubber mallet jumps the pins for a split second. Silent, tool-free and leaves almost no trace. Targets basic pin-tumbler cylinders.
6%
of forced entries
Tension wrench plus picks. Rarer than films suggest — takes real skill and quiet access. More common on older mortice locks than on patented modern cylinders.
14%
of break-ins
Self-tapping screw driven into the cylinder, then a slide hammer yanks the whole cylinder out of the door. Works on exposed, projecting cylinders.
24%
of forced entries
Crowbar between door and frame, or repeated hard kicks once the cylinder has been defeated. The failed multi-point gearbox is the common enabler.
Tick these ten items before you spend a pound. Every professional locksmith in the UK works through a version of this before quoting.
A missed Kitemark can void a burglary claim. This is the part of lock buying homeowners find boring and insurers find essential — so we'll keep it short and real.
That one sentence appears in some form on almost every home policy sold in the UK. "Final exit doors" means any door you could leave the house through. "Kitemarked equivalent" is what makes TS007 3-star and Sold Secure Diamond cylinders acceptable on modern uPVC and composite doors where a mortice would be impossible to fit.
If yes, claim continues. If the door was unlocked, most policies refuse.
Loss adjuster checks each external door for Kitemark / standard number.
A rotten frame or a dropped multi-point door counts as "not properly secured".
In practice this means: insurance-approved locks on every external door, maintained frames and hinges, and a working multi-point mechanism. If you're not sure what you have, every Locksmith South London visit includes a free security audit — we walk each external door, identify the locks, list the gaps, and email you a written summary you can attach to your policy file.
Repeated in neighbourhood WhatsApp groups, on Reddit and by well-meaning hardware-shop staff. Here's what's actually true.
Only the versions that carry the Kitemark plus TS007 3-star or Sold Secure Diamond have been tested against the attacks above. Buy the rating, not the logo.
Deadbolt is American terminology (single-throw, key both sides). In the UK, a deadlock is a BS3621 mortice lock with five levers. Don't buy imported hardware labelled "deadbolt" for an insurance-compliant door.
A smart lock is as secure as the cylinder underneath it. Most pure smart locks have a plastic gearbox that a cordless drill defeats in 30 seconds. Always layer on a 3-star core.
That's a thumb-turn cylinder, which is a convenience feature (lock from inside without a key). It doesn't add security — and on a door with a glass panel, it's a burglary risk. See our thumb-turn cylinder page for when to fit one.
Housebuilders often fit the cheapest compliant cylinder, then replace it with 1-star cylinders during snagging. Check the rating yourself — it's stamped on the cylinder body.
Key control is useful — it stops copies walking out of the office — but it doesn't stop snapping, drilling or kicking. The lock body is what survives a forced attack, not the key.
These don't make it into competitor articles but they save our customers real money every week.
Budget-constrained? Spend on a 3-star cylinder and a working multi-point gearbox before you buy any smart CCTV or alarm. A locked door they can't breach is worth ten cameras recording them leaving.
90% of homeowners buy the wrong size cylinder on Amazon and pay to fit a mismatched one. Open the door, photograph the lock edge-on, and send it to us or your chosen locksmith — we'll confirm the size in seconds.
If you just moved in, ask for the front, back and side doors to be keyed-alike and rekeyed together. One visit, one key, and any previous copies the seller or estate agent kept become useless.
A dry cylinder is 10% harder to pick and 100% easier to snap. Use a graphite or dry PTFE lubricant — never WD-40. Two puffs into the keyway each autumn doubles lock lifespan.
Genuine customer feedback from real lock upgrades across SW, SE, CR and BR postcodes. Rated 5.0 on Google.
Insurance renewal flagged my cylinder as non-compliant and I didn't know where to start. Daniel came out the same day, fitted a Brisant Ultion 3-star on my composite door and emailed the written spec I needed for the underwriters. Insurance premium actually came down £47 on the year.
Victorian terrace, original timber front door, landlord asked for BS3621. Booked online, engineer arrived on time, fitted a Union 2134E mortice and a Kitemark-compliant nightlatch with keyed-alike. Clean work, swept the shavings, and gave me a card to pass to the letting agent.
Wanted an Ultion Nuki for the school-run convenience but didn't want to compromise the cylinder. Thomas walked me through the options on the driveway, showed me what 3-star meant up close, and fitted everything in under an hour. App works with HomeKit, my wife loves the auto-lock, my insurer is happy.
The questions UK homeowners actually ask us before upgrading their locks — answered honestly, with no upsell.
For timber doors, a BS3621 5-lever mortice deadlock is the most secure choice — Union 2134E, Chubb 3G114 or ERA Fortress are all trade standards. For uPVC and composite doors, a TS007 3-star anti-snap euro cylinder paired with a high-security multi-point mechanism is the benchmark.
Both options meet UK insurance requirements and resist snapping, drilling, picking and bumping. The right answer depends on your door material, not brand preference.
Most UK home insurers require BS3621-certified locks on all final exit doors — the front door, any back door, and any door off an attached garage. Without them, a claim after a burglary can be argued, reduced or refused outright.
Check your policy wording — look for "British Standard" or "BS3621" in the security clauses. On modern uPVC and composite doors where a mortice won't fit, most policies accept a TS007 3-star cylinder or Sold Secure Diamond equivalent. Full detail on our insurance-approved door locks page.
Yes, every time. Lock snapping accounts for roughly 27% of UK domestic burglaries and takes seconds on a cheap cylinder. A TS007 3-star cylinder (or a 1-star cylinder plus a 2-star handle) stops the attack dead and typically costs around £200 fitted by a working locksmith.
Compare that to the average £3,800 burglary loss (ABI 2025 figures) plus the emotional cost, and the upgrade pays for itself eighteen times over.
Neither is inherently "better" — they suit different doors. Mortice deadlocks go in timber doors and are graded by BS3621. Euro cylinders go in uPVC and composite doors and are graded by TS007 and Sold Secure.
Matching the lock to the door material is what matters. On a timber front door, fit a BS3621 mortice. On a uPVC back door, fit a TS007 3-star cylinder. Forcing the wrong lock onto the wrong door weakens both.
Only if the smart lock is layered over a high-security mechanical cylinder. The popular UK choices — Ultion Nuki, Yale Linus, August — rely on the underlying cylinder for security. Fit a TS007 3-star anti-snap cylinder first, then add the smart module.
Never replace a BS3621 mortice with a purely electronic lock on an insured door — you'll void the policy. See our smart door locks guide for the full comparison.
TS007 is a star rating (1–3 stars) for euro cylinders and door furniture, focused on snap, pick, drill and bump resistance. Sold Secure is an independent testing tier (Bronze, Silver, Gold, Diamond) covering a wider range of security products — cylinders, padlocks, chains, safes.
A Sold Secure Diamond cylinder is broadly equivalent to a TS007 3-star cylinder. Most UK insurers accept either rating on modern doors.
Locksmith South London fixed prices:
TS007 3-star anti-snap cylinder fitted — from £200. BS3621 5-lever mortice deadlock fitted — from £180. Standard euro cylinder replacement — from £135. Multi-point gearbox repairs — from £350. Night latch replacement — from £250.
Complex uPVC repairs and smart lock installs are quoted on WhatsApp after a photo — full price list on our lock replacement cost page.
Open the door and look at the lock faceplate on the door edge — a Kitemark (the BSI heart-shape logo) should be stamped into the metal, not a sticker. "BS3621" is usually engraved on the bolt itself.
If you can't see either, assume it's not certified. Our engineers carry a pocket guide to every BS3621 brand and can identify yours in under a minute on a free visit — see the BS3621 locks page for the visual identification guide.
Go deeper on any mechanism or standard covered above — every link below is a proper in-depth page, not a filler stub.
The lock snapping epidemic, TS007 3-star, and the brands that actually stop it.
Read guide StandardsKitemark identification, insurance clauses, and the 5-lever pattern to buy.
Read guide BlogEvery UK door lock in one walkthrough — mortice, cylinder, nightlatch, rim, smart.
Read guideSend a photo of your existing lock and door edge on WhatsApp — we'll reply with the right spec, a fixed price, and a slot. No call-out fee, no VAT on quoted prices, card, cash or bank transfer.
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