Scrump wrote:
I don't think such a lock exists

http://www.liftandlock.com/

(I've sent them an email, but want an opinion from uk.d-i-y)

lots of people with them
falsely believe the door locks when you lift the handle, and
get burgled as a result of it not actually being locked at all.

That is exactly what has just happened to us!

So can a second person unlock the door with a key once this lock has
been "locked" from the inside?
If not this could be a real PITA in our household.

Bob