Traindriver69

Hi all Just picked up a 2004 cooper s and discovered it has a central locking problem with just the drivers door. If you press unlock on the remote passenger door and boot unlock but not the drivers door so have to use the key in the lock but once open if you press lock the door locks but if you sit inside the car and press lock it won't lock nor will it lock with the interior switch or when you start off driving the car, Any ideas?. Many thanks in advance.