Mortice deadlocks and euro cylinders are the two most common lock types on UK homes. They suit different door types, carry different security standards, and have different insurance implications. Here is how to tell which you need.
The Two Most Common Door Lock Types in UK Homes
Walk down any street in Dulwich, Camberwell or Peckham and the external doors will mostly use one of two primary lock types: a mortice deadlock set into the door body, or a euro cylinder sitting within a lock case. Understanding the difference matters because they have different security profiles, suit different door constructions, and have different implications for home insurance.
Mortice Deadlocks
A mortice deadlock is set (morticed) into the door itself — the lock mechanism sits inside the door body. You operate it with a key from outside. The most security-relevant variety is the five-lever mortice deadlock meeting BS3621:2007+A2:2012.
Five levers means the mechanism has five components that must align correctly for the key to work — this directly increases pick resistance compared to three-lever variants. A BS3621-certified five-lever mortice has been independently tested against picking, drilling, sawing and key profiling attacks.
**Best suited for:** Traditional timber doors — Victorian and Edwardian terraces, wooden rear and side doors. Most South London period properties use mortice deadlocks as the primary securing mechanism on back and side entries.
**Insurance:** Most UK home insurance policies explicitly require BS3621 five-lever mortice deadlocks on timber external doors. Fitting anything less may void a claim.
Euro Cylinder Locks
A euro cylinder is the oval-shaped barrel that operates via a key on one or both sides. Euro cylinders fit within a lock case and are found in virtually all UPVC doors, composite doors, and many modern wooden doors using a multipoint locking system.
Standard euro cylinders are vulnerable to cylinder snapping — the most common urban burglary technique. Anti-snap cylinders rated TS007 3-star are designed to resist this attack by incorporating a sacrificial break point that leaves the door locked even when the outer section is removed.
**Best suited for:** UPVC and composite doors, modern wooden doors with multipoint systems.
**Insurance:** A TS007 3-star anti-snap cylinder within a multipoint mechanism is accepted by most insurers as the UPVC and composite door equivalent of a BS3621 mortice.
Which Does Your South London Property Need?
Unsure what you have or what you need? Call 07984 547185 — we will assess your doors and give honest advice.