This is a very good answer. The last part is probe to discussion, though. You need to make the lock weaker, yes, but maybe just a little bit and you maybe need

This is a very good answer. The last part is probe to discussion, though. You need to make the lock weaker, yes, but maybe just a little bit and you maybe need 4.5 days to open it vs. the 5 days when there is no master key. It is a matter of math (mechanics in that case) and risk assessment.