But how many BS3621 mortice locks would need to be fitted to achieve an equivalent level of security and load distribution as a modern multi-point locking system on a composite door, John? A BS3621rated mortice lock may meet a recognised security standard, but ultimately it remains only as strong as the surrounding door construction and the frame retaining the striker plate.
Early in my career, when I was involved in emergency glazing, boarding-up work and basic locksmithing, I spent a considerable amount of time repairing forced entry damage to timber doors and frames as well as uPVC. I was by no means a master locksmith, but I knew my way around picking a mortice lock and drilling or snapping a standard euro cylinder where necessary. I lost count of the number of split timber door stiles I had to glue and screw back together, or the number of damaged frames that required splicing and reinforcement before a striker plate could be refitted. In most cases, the lock itself had not failed; the surrounding timber had. Yet in over 16 years working in that industry, I can honestly say I never encountered a single euro cylinder that had been attacked in situ. That's not to suggest cylinder attacks do not occur, because lock snapping became a well documented issue in later years, but it's worth noting that euro cylinder technology has evolved significantly since the 90s and early 2000s.
Anti-snap, anti-bump and anti-drill cylinders have been widely available since around 2010, and the market today ranges from basic budget cylinders costing less than £10 through to TS007 3-star accredited cylinders exceeding £100. All of that is positive progress, but it doesn't alter the fundamental engineering principle: the security of any locking system is ultimately limited by the strength of the door and frame to which it is fitted. A multi-point locking system spreads loads across multiple locking points along the full height of the door, reducing the concentration of force at a single location.
By comparison, a traditional mortice lock secures the door at one primary point, meaning the surrounding timber and frame are required to withstand far greater localised loading during an attempted forced entry. In simple terms, the lock specification is only one part of the security equation. The overall performance of the system depends on the lock, the door leaf, the frame, the keeps, the fixings and how effectively they work together under attack.
