Lathams door handle functionality
If you just shut the door, it isn't locked.
If you then turn the handle up from the outside it is locked and can be unlocked from the inside without a key or it can be unlocked from outside with a key.
If you had shut the door and turned the key just ONCE from the outside, it can be unlocked from the inside without a key or it can be unlocked from outside with a key.
If you had shut the door and turned the key TWICE from the outside, it can be only unlocked from the inside with a key/thumbturn cyclinder (if that was available for your lock) or it can be unlocked from outside with a key.
if you had shut the door and turned the handle up from the inside, it is locked and can only be unlocked from the outside with a key or it can be unlocked from inside without a key.
Q:What about the thumbturn I can see in the video at the bottom of the inside face of the lock? Does that engage a lock from the inside that can't be unlocked from the outside at all (even with a key)?
A: The lock on the inside bottom is a privacy lock, a bit like a bathroom door lock, it can only be engaged/opening from the inside
