Abstract: A locking mechanism for a mobile safe having at least one loading door for depositing valuables such as cash within the safe and at least one unloading door for emptying the safe includes an actuating mechanism for moving the loading door between its open and closed positions. The actuating mechansim extends out of the safe for engagement with a vault door locking mechanism when the safe is placed within an outer vault for secure deposit of cash into the safe. The engagement is such that the actuating mechanism operates to open the loading door as the vault door is locked. A locking device associated with the actuating mechanism automatically locks the safe door in its closed position and can only be released by subsequent unlocking or opening of the unloading door by a person having the required key.