Earlsfield Locksmith Service Team
Local locksmith team
7 Oct 2026 11 min read
If you look at most front doors in Wandsworth — along Garratt Lane, the terraced streets off Earlsfield Road, or the mansion-block flats near Tooting — you will usually spot two locks, not one. There is a springlatch up near the handle, and a keyhole lower down. Many homeowners use them both every day without giving them a second thought, until one stops working or they find themselves locked out. Understanding what each lock actually does, and why both matter, is the fastest way to know whether your door is properly secured and what to ask for when something goes wrong.
This guide explains the mortice lock and the nightlatch in plain terms — how each one works, the British Standards that insurers care about, and when you genuinely need both. If you are dealing with a lock problem right now and need a locksmith London homeowners and tenants in Wandsworth can call any time of day or night, ring us on 020 3757 5840 and we will talk you through it straight away.
## What Is a Mortice Lock, and Why Does It Live Inside the Door?
[7] A mortice lock is fitted into a pocket — the mortice — that is cut directly into the edge of the door. Because the mechanism is recessed inside the timber, the lock cannot simply be prised off the surface; the door itself has to be defeated before the lock body is reached. That structural integration is the main reason a mortice lock is considered a serious security device rather than a convenience latch. When you turn the key, a solid steel bolt shoots sideways into a metal keep (the striker plate) in the door frame. That bolt, called a deadlock bolt in British usage, stays put until a key turns it back. There is no spring — the bolt does not retract if you push or pull the door — which is what makes it a true deadlock.
Mortice locks come in lever grades. A 2 lever mortice lock is simple and inexpensive, but it offers only basic security and is generally not acceptable to home insurers for an external door. A 5 lever mortice lock is the grade your insurer almost certainly specifies; the five levers inside the case each need to align correctly before the bolt will move, making picking considerably harder. The gold standard for UK front doors is a 5 lever mortice lock that also carries the BS3621 kite mark, which means it has been tested to a British Standard for security. If your policy wording says 'BS3621 deadlock', a 5 lever mortice lock with that kite mark is what you need.
## What Is a Nightlatch (and What Is a Rim Lock)?
The upper lock — the one that clicks shut automatically when you pull the door behind you — is called a nightlatch, often referred to colloquially as a Yale lock after the brand name that became generic. Technically it is a rim lock, because the cylinder and latch mechanism are mounted on the surface (the rim) of the door rather than recessed into it. If you have ever wondered 'what is a rim lock?' or heard someone mention a rim cylinder, they are both describing this surface-mounted family of locks. The cylinder — the barrel that your key turns — sits through the door, and the latch body is screwed onto the inside face. When the door closes, a bevelled springlatch snaps into the keep automatically, which is why you do not need to turn a key to lock up as you leave.
The convenience of an automatic latch is also its limitation. A standard nightlatch can be held back with a credit card or a strip of plastic if the door fits badly, and the cylinder can be pulled or snapped if it protrudes too far. Modern anti-snap, anti-pick cylinders in a TS007 3-star rating address most of those vulnerabilities, and fitting one is a worthwhile upgrade on any external door. On uPVC and composite doors the nightlatch is replaced by a euro cylinder that drives a multipoint lock — a different arrangement, but the same underlying idea of a quick-latching mechanism for everyday use alongside a more serious locking mode engaged by lifting the handle or turning a key.
## Why Most UK Front Doors Need Both — and When One Is Not Enough
The two locks serve genuinely different purposes and work together as a system. The nightlatch handles convenience: you slam the door, it locks itself, and you are off. The mortice deadlock handles security: before you go to bed, or when you leave for more than a few minutes, you turn the lower key and the bolt shoots home. Many insurers require both to be engaged for a contents claim to be valid after a break-in. Using only the nightlatch is a bit like fastening just the top button of a coat — it looks fine until conditions turn against you.
There are common situations where one lock quietly stops doing its job. A nightlatch that has not been double-locked (most have a small internal lever that deadlocks the latch so it cannot be pushed back) is surprisingly easy to defeat on a poorly fitting door. A mortice lock that has not been serviced in years can develop a fault where the bolt does not fully extend — it looks locked from the outside but the bolt is only halfway into the keep. If you are unsure whether your existing locks are both working correctly and meeting your insurer's requirements, our team offers a lock assessment as part of any call-out. We cover lock change London requests across Wandsworth and surrounding areas, and we can confirm on the phone what parts, if any, would be needed before anyone comes out.
## uPVC and Composite Doors: A Different Setup, the Same Principle
Older timber front doors follow the classic two-lock pattern described above. Most doors fitted in the last twenty years, however, are uPVC or composite, and these use a multipoint locking system driven by a euro cylinder. Instead of a separate nightlatch and mortice, lifting the handle throws multiple bolts and hooks simultaneously, and the euro cylinder deadlocks them all in one turn. It is an elegant system, but it does introduce the euro cylinder snap risk: if the cylinder protrudes more than a few millimetres beyond the door furniture, it can be snapped with a cheap tool bought online, allowing the door to be opened in seconds.
Anti-snap cylinders are the direct answer to this. Look for cylinders rated TS007 3-star or at least TS007 1-star combined with a 2-star door handle — insurers and police crime-prevention officers across the UK have recommended this combination for years. If you have recently moved into a property in SW17, SW18, or the surrounding postcodes and are unsure what cylinder is currently fitted, that is worth checking before anything else. Our team handles door lock replacement London wide, including upvc door lock repair London calls where the cylinder has snapped, the multipoint mechanism has seized, or the handle has dropped. We carry common cylinder sizes and can usually resolve the job in a single visit.
## Locked Out, or Suspecting a Fault? Here Is What to Do First
If you are locked out London residents should follow a few sensible steps before calling a locksmith. Check whether anyone else holds a spare key — a family member, neighbour, or letting agent. Try any other door into the property; a back door or ground-floor window might be accessible safely and legitimately. If you are a tenant, your landlord or managing agent may hold a key and may have a duty to assist outside of office hours depending on your tenancy agreement. If none of those options applies, the next step is to call a professional. We are an emergency locksmith London residents in Wandsworth and the surrounding area rely on around the clock, and we will ask you a few questions to verify your connection to the property before any work begins — that is standard practice and entirely reasonable.
When you call 020 3757 5840, we confirm an exact up-front price before we come out, so there are no surprises on arrival. The final quote depends on factors such as the lock type, the complexity of the work, the time of day, any parts needed, and travel distance — we explain all of that on the phone. We send a locksmith straight away and are usually with you in about 30 minutes. For non-emergency situations — such as upgrading from a 2 lever mortice lock to a BS3621 5 lever mortice lock, fitting an anti-snap cylinder, or repairing a dropped handle on a uPVC door — just give us a ring and we will arrange a convenient time. We operate as a 24 hour locksmith London service, which means evenings, weekends, and bank holidays are all covered.
## 25 Services We Provide Across Wandsworth and the Surrounding Area
Our mobile team handles a wide range of residential lock and door work, including: emergency lockout assistance for houses and flats; non-destructive entry where the lock can be preserved; lock change London for all door types; fitting BS3621 5 lever mortice deadlocks; replacing worn or damaged 2 lever mortice locks with higher-security alternatives; installing and replacing nightlatches and rim locks; anti-snap euro cylinder supply and fitting; TS007 3-star cylinder upgrades; full door lock replacement London for timber, uPVC, and composite doors; multipoint lock repair and replacement; dropped handle repair on uPVC doors; upvc door lock repair London including gearbox and mechanism replacement; door alignment and adjustment where the frame or slab has dropped; fitting new door furniture including handles, escutcheons, and letterbox plates; security assessments for homeowners and tenants; lock changes after a tenancy change or lost key; fitting extra security bolts to sliding patio doors and French doors; fitting hinge bolts to outward-opening doors; communal entrance lock repair for blocks of flats; door reinforcement to address weak strike plates; Yale-type nightlatch replacement and upgrade; cylinder removal for snapped or damaged euro cylinders; lock maintenance and lubrication for stiff or sluggish mechanisms; advice on BS3621 compliance for insurance purposes; and 24-hour callout across all Wandsworth postcodes for genuine emergencies — with an up-front price confirmed before we travel.
Frequently asked questions
What is a mortise lock, and is it the same as a deadlock?+
A mortise lock (also spelled mortice in British English) is a lock that fits inside a pocket cut into the door edge, so the mechanism is entirely concealed within the door. When the key turns, a solid steel bolt shoots into the door frame — and because there is no spring, that bolt stays put until a key retracts it. That is why a mortice lock is also called a mortice deadlock: the bolt is dead, meaning it cannot be pushed back by pressure alone. It is different from a nightlatch, where a spring-loaded bevelled latch snaps shut automatically. For external doors, insurers typically require a 5 lever mortice lock that meets BS3621.
What is a rim lock, and how is it different from a mortice lock?+
A rim lock is a lock whose body is screwed onto the surface — the rim — of the door rather than recessed inside it. The classic nightlatch is a rim lock: the cylinder goes through the door, and the latch case sits on the inside face. The difference from a mortice lock is structural. A mortice lock is hidden inside the door timber, which makes it very difficult to attack from outside. A rim lock is exposed on the surface, which is why the quality of the cylinder and the door furniture around it matters a great deal. Modern anti-snap, anti-pick cylinders significantly improve the security of a rim lock setup.
Do I need both a nightlatch and a mortice lock on my front door?+
For most standard timber front doors in the UK, yes. The nightlatch gives you everyday convenience — the door locks itself when you close it — while the mortice deadlock provides the structural security that insurers and police crime-prevention guidance both recommend. Many home insurance policies require both to be engaged for a claim to be valid if the door is forced. If your door is uPVC or composite with a multipoint lock, the system works differently, but the principle is the same: you need a secure deadlocking mode in addition to the automatic latch. If you are unsure what your door currently has, or whether it meets your insurer's requirements, give us a ring on 020 3757 5840 and we can advise you.
How do I know if my euro cylinder is at risk of snapping?+
The main risk factor is how far the cylinder protrudes beyond the door furniture. If more than a few millimetres of the cylinder barrel sticks out past the escutcheon or handle plate, it can be gripped and snapped with a simple tool. Check this by looking at the edge of your handle plate on both sides of the door — the cylinder should sit flush or just within the plate, not protruding noticeably. If it does protrude, or if you do not know when it was last replaced, upgrading to an anti-snap cylinder rated TS007 3-star is a straightforward and worthwhile job. We carry a range of cylinder sizes and can assess and replace yours in a single visit across the Wandsworth area and beyond.
