A locking mechanism is provided for use with at least one access door (10) of a building, the mechanism comprising at least one operating handle (12) and at least one electrical operating device (14), the locking mechanism having a first internal device (12) manually operable to activate electrical means of the locking device, and the second internal device (19) manually operable to override the electrical means of the locking device to open the door, the locking device including at least one security locking mechanism (80) operable by the first to internal device (12), release of the security locking mechanism (80) not being possible by operation of the second internal device (19). The invention provides added security under certain conditions, for example when a householder is away on holiday.