An estate agent asked me to help tenants in a top-floor flat in Isleworth after the front-door nightlatch failed and they became stuck inside.
The tenants could not turn the lock from inside, and the keys were also in poor condition and difficult to engage from outside.
After checking the key operation and trying the obvious non-destructive options, it became clear that the deadlocking section of the nightlatch was the main problem.
With the tenants still inside, I talked them through releasing the failed section from their side of the door. That avoided having to destroy the lock from outside just to gain access.
Once the door was open, the old nightlatch was clearly past the point where I would have trusted it to continue in service.
I replaced the complete backbox and rim lock, made the necessary adjustments and tested the operation from both sides.
The tenants had working access again and a new set of keys for the replacement lock.
