Door lock

A security system comprising:

• a locking apparatus for a door, said locking apparatus comprising a lock, a key and a sensor which detects whether the door is in a closed position, wherein the key is engageable with the lock at a first side of the door so as to enable the door to be unlocked and the key is subsequently removable from its engagement with the lock only at a second side of the door remote from the first side, wherein the key is only removable, once engaged in the lock, when the sensor senses that the door is in a closed position, and wherein removal of the key causes locking of the door;
• a door on which said lock apparatus is mounted;
• a detector means for detecting the presence of a user;
• and
• a computer control unit capable of receiving data from the detector means and from the key and of controlling the lock apparatus, wherein the key is only removable from the lock when data passed from the key to the computer control unit correlates with data passed from the detector means to the computer control unit.