Rover 820i Central locking?

If the drivers lock is damaged, then the central locking will be trying to turn it from inside. It can't do so, so the system senses that it (being the "master" lock) is unlocked and opens the others.

I suspect they're probably similar to the system on the 218, in which case they're not too difficult, though a little fiddly. You'll have to remove the door trim and probably the bolt at the bottom of the window channel to gain access. There'e a metal rod to the locking motor which clips into a linkage on the back of the lock barrel; unclip this as a temporary fix. The barrel itself is easy enough to replace, but you'll probably need to remove the door handle to get enough access; this is the fiddliest bit. There are two nuts inside the door skin (ISTR you'll need to wind the window down a bit to access one of them). The handle can then the jiggled out - care not to break it. The barrel fits in with a spring clip.

It's a job I've done several times as the motors are prone to failure!