What Are High-Security Locks and When Do You Need Them?
High-security locks are locks independently tested and certified to resist forced entry methods including picking, drilling, bumping, and snapping. In the UK, the key standards are BS3621 for mortice locks on timber doors and TS007 3-star for euro profile cylinders on uPVC and composite doors. Most UK home insurers require BS3621 or an equivalent standard on all external doors - failing to comply can invalidate a claim. Upgrading to a certified lock is one of the most effective and cost-efficient steps you can take to protect your home or business.
What Makes a Lock “High Security”?
Not all locks labelled “high security” are independently certified. The meaningful distinction is whether a lock has been tested against a published British or industry standard and carries the relevant mark - the BSI Kitemark, Secured by Design, or Sold Secure.
In practical terms, a high-security lock differs from a standard lock across five areas:
1. Hardened Materials
High-security locks use hardened steel components throughout the mechanism. This resists drilling - a common forced-entry technique - and extends the working life of the lock.
2. Advanced Internal Mechanisms
Standard pin tumbler locks use a relatively simple arrangement of spring-loaded pins. High-security equivalents add sidebars, anti-pick pins, spool pins, and other features that make manipulation significantly harder. These mechanisms cannot be defeated by the bump key or basic picking techniques that open standard locks.
3. Key Control
Many high-security locks use patented key blanks that can only be duplicated by authorised dealers with proof of ownership. Even if someone obtains your key, they cannot copy it at a high-street kiosk.
4. Anti-Drilling Protection
Hardened steel pins or anti-drill plates are positioned at critical points within the lock body. When a drill bit strikes these components, it deflects rather than biting.
5. Anti-Snap Design
Euro cylinders fitted to uPVC and composite doors are particularly vulnerable to snapping. High-security cylinders include a sacrificial break point that separates when attacked, leaving the internal cam - and your door - secure.
UK Lock Standards and Ratings Explained
Understanding the certification labels helps you choose the right lock and satisfy your insurer.
| Standard | Applies To | What It Tests | Key Benefit |
|---|---|---|---|
| BS3621 (latest: 2017+A1:2024) | Mortice deadlocks, rim nightlatches (timber doors) | Picking, drilling, sawing, key-bumping; min. 5 levers, 20 mm bolt throw | Required by most UK home insurers |
| TS007 1-star | Euro cylinders (uPVC/composite doors) | Drilling, picking, bumping - but NOT snapping | Must be combined with 2-star handles |
| TS007 3-star | Euro cylinders | Anti-snap, anti-drill, anti-pick, anti-bump, plug extraction | Highest cylinder rating; insurers accept as stand-alone |
| Sold Secure SS312 Diamond | Euro cylinders | Same scope as TS007 3-star; 5 min attack resistance incl. angle grinder | Considered equivalent to Kitemark 3-star |
| Sold Secure Gold/Diamond | Padlocks | Progressive attack resistance; Diamond = 5 min specialist tools | Used for gates, outbuildings, vehicle security |
| Secured by Design | Doors, windows, hardware | Police-endorsed specification for residential and commercial use | Reduces burglary risk; recognised by some insurers |
Quick rule: For a timber front door, look for the BSI Kitemark and the BS3621 number stamped on the faceplate (visible when the door is open). For a uPVC or composite door, look for the Kitemark and “TS007 3-star” on the cylinder end cap.
Does Home Insurance Require Specific Locks?
Yes - this is one of the most misunderstood areas of home security. Most UK home insurers include a locks clause in their policy conditions that specifies:
- All external ground-floor doors must be fitted with a BS3621 mortice deadlock or equivalent.
- For uPVC and composite doors, a TS007 3-star cylinder or equivalent (such as Sold Secure SS312 Diamond) is typically accepted.
- Patio and French doors are usually required to have multi-point locking.
If your locks do not meet the required standard and you suffer a break-in, your insurer can reduce or refuse your claim - even if nothing was technically wrong with the lock when the break-in occurred.
Some insurers also offer a premium discount for locks that exceed the minimum standard - for example, Secured by Design certification or electronic access control on commercial properties.
Always check your specific policy wording. The latest version of BS3621 is BS 3621:2017+A1:2024, but even older BS3621 versions are generally accepted.
Types of High-Security Locks
High-Security Mortice Deadlocks
The traditional choice for timber front and back doors. A BS3621 five-lever mortice deadlock is the standard requirement. Brands such as Yale, Banham, Ingersoll, and ERA manufacture Kitemarked versions at a range of price points.
For higher-risk properties, cylinder mortice deadlocks from Abloy or Mul-T-Lock add patented key control on top of the BS3621 base certification.
TS007 3-Star Euro Cylinders
The most important upgrade for the majority of London homes with uPVC or composite doors. A standard euro cylinder can be snapped with basic tools in under 30 seconds. A TS007 3-star replacement cylinder is a direct swap - no door modification required - and provides anti-snap, anti-pick, anti-drill, and anti-bump protection.
Our guide to replacing a barrel lock in a uPVC door explains how cylinders work and what to look for when choosing a replacement.
For a broader comparison of lock types and security ratings, see our guide on the best front door locks for UK homes.
High-Security Padlocks
Closed-shackle design - which exposes far less of the shackle to bolt-cutters - combined with a Sold Secure Gold or Diamond cylinder makes for a highly resistant padlock. Suitable for gates, outbuildings, garage side doors, and storage units. Look for a CEN4 rating or above alongside the Sold Secure grade.
Electronic and Smart Locks
High-security electronic locks combine physical resistance with digital access control. Codes can be changed instantly, audit logs record every entry, and biometric models ensure only enrolled users can gain access. These are increasingly common in commercial environments and some residential properties. See our guide to smart locks for UK homes for current options.
When Do You Need High-Security Locks?
Your Home Insurance Requires It
As covered above, BS3621 and TS007 3-star are standard insurance conditions. If you are not sure whether your current locks comply, a lock change assessment from a qualified locksmith will clarify the position quickly.
After a Break-In
A break-in - whether or not entry was forced - is the right moment to reassess your entire door security, not just replace the damaged component. Our break-in repair service includes a security audit as standard.
Your Door Has a Standard Euro Cylinder
If your uPVC or composite door has a cylinder without a TS007 or Sold Secure marking, it is almost certainly snappable. This is one of the highest-probability risk factors for residential burglary in London.
You Own a Second Property or Holiday Let
Properties that stand empty for extended periods are disproportionately targeted. High-security locks combined with a monitored alarm significantly reduce risk.
You Hold High-Value or Sensitive Contents
Art, jewellery, specialist equipment, and confidential records all increase the cost-benefit ratio of investing in certified hardware. Insurers may also specify higher standards for contents policies covering items above certain values.
Commercial and Business Premises
Businesses have additional drivers beyond personal security:
- Retail and hospitality with high-value stock or cash on site
- Professional services (law firms, accountants, medical practices) with confidential client data
- Warehousing and logistics where stock values are significant
- Server rooms and data centres where physical access control is a regulatory requirement under ISO 27001 or similar frameworks
A door lock installation on commercial premises should include a review of masterkey systems, access levels, and audit logging requirements alongside the hardware specification.
What to Look for When Buying a High-Security Lock
- Check the Kitemark - the BSI Kitemark on a lock confirms independent third-party testing, not just a manufacturer claim.
- Match the standard to your door type - BS3621 for timber mortice locks; TS007 3-star for euro cylinders.
- Measure the cylinder correctly - a euro cylinder fitted too long is still snappable at the protruding end. Measure the cylinder so it sits flush with or just inside the door furniture.
- Consider key control - if key management matters (rented property, shared access), a patented key profile adds meaningful security.
- Check your insurer’s wording - some policies name specific standards; others accept equivalents. When in doubt, call your insurer before purchasing.
Our lock price list sets out the current rates for supply and installation, including high-security cylinders and mortice locks. Lock change labour starts from £69; fresh installations from £89 per hour (prices ex VAT, no call-out fee, free quotes).
Working With a Professional Locksmith
The correct specification matters as much as the quality of the hardware. The wrong cylinder length, an insufficiently deep mortice pocket, or a misaligned strike plate can undermine even the best lock. City Locksmith London has been fitting high-security locks across Greater London for over 15 years, with fully insured and DBS-checked engineers.
For a comparison of all lock and window security types we work with, see our guide to door and window lock types.
To discuss the right specification for your property, contact us directly for a free assessment. We respond within 25 minutes, 24 hours a day, across all London postcodes.