Well I don't understand this;

I was not allowed to have a mortise lock fitted because it is theoretically possible to be locked in if someone with a key locks the door from the outside.
Exactly the same is possible with this lock. Apparently that's OK because I live alone and nobody else has a key.
Ummm  .  .  .
Does that suggest to you that a mortise lock must therefore come complete with a live-in companion?
Not only that, but if this lock were locked from the outside, it is then impossible to unlock it from inside, even with a key.
And, this latch has the potential to shut me out if the door were to blow shut in a breeze while I am in the bathroom without my front door keys. And that means I must keep my keys in one of the two locks, which is apparently not advised.

I was also told that an exit door must not require two hands to open it. This one now does. It wouldn't require two hands if it had a mortise and not a night latch, or if the latch had replaced the handle instead of being an addition.

I wish I had been allowed to have Tony carry out the work.