Most organisations have someone who knows the site better than everyone else.

A real emergency does not create one problem. It creates several problems at once, often for teams with very different responsibilities.

Emergency plans have to be exercised.

Recovery & Learning.

An emergency plan rarely depends on one action. It depends on communications working, site access remaining available, equipment being operational, staff being present and outside support arriving when expected. That creates dependencies. A tabletop exercise should test them.