What the heck is this door catch thing for?

[minisandfords]

My drivers side rear door keeps clunking when you shut it- it seems to be catching on this thing? 
Any idea what it's for? Looks like the metal engages with a catch on the actual door, but there is a cable attached to it too? Even weirder, it's only got one on the drivers side, not passenger?

Very odd, and quite annoying as it seems to be stopping door from shutting properly first time!

[Tomcat3]

Is it to do with the fuel tank cap, you are not ment to be able to open the offside rear door when the cap is off.

[Trevor]

Tomcat is of course correct. Your missing a cover plate from it, below is the Mk3 version if the door it catching it, it must be in need of adjustment.

[minisandfords]

Aha, mystery solved! That makes a lot of sense, thanks! Never tried to open door with fuel cap off!

I have the cover plate, I had removed it to look inside.

So, how do I adjust it then? Any ideas?

[Tomcat3]

Why do you need to adjust it?????? To see if its working properly have the offside door shut and remove the fuel cap then try and open the door. You shouldn't be able to open it.

[minisandfords]

It's catching as the door shuts- you can feel it banging on the door as the door closes, so I don't think it's catching right.

[Tomcat3]

Has one of the door rollers broken or twisted causing the door to run closer to the frame or something.