Thanks Eleanor. Does anyone here have a front door which locks just by closing it, and can then be optionally double-locked by inserting key and turning it? When double-locked, can it be opened from inside without key please?
Our locks were like that in Germany. If you just closed it when you went in you could open it from inside and go out without a key. Anyone left outside when the door was closed needed a key to get in. If you double locked it on the inside at night you needed to unlock it in the morning to get out.
The couple in 5L told the bookkeeper they left their door 'on the latch'. This would not allow anyone to get in, but they could get out if they were already in. The T7 children were double-locked in, so couldn't get out.
If someone left the key in the door on the inside I would think it couldn't be opened with a key from the outside. Because the 'turning' bit of the mechanism is filled, the outside key wouldn't get to it.