"Don't touch that fuse!" Oh Oh, too late.

[Alansdad]

Hi, I am a new member and a new owner of a Rover 75 tourer diesel. I am very happy :lol: to find this site and hope I can sort some problems out with your help.
My battery is draining flat if I leave the car for a couple of days. I checked the current flow with "everything switched off" and found a 2.5 to 3 amp flow which I traced to a 50 amp fuse in the engine compartment fuse box. It is not an ordinary plug in fuse. It is one of the fuses held in with two screws. The diagram on the cover of the fuse box just has a picture of an engine for that fuse.
The owners manual calls those fuses "fusible links" and says nothing more about them other than advising owners not to touch them and leave it to a qualified electrician.
Ooops! In my enthusiasm to find the power leak I removed each fuse, one at a time and tested with an amp meter. I have removed the 50amp fuse for a couple of days to see if the battery will be ok when I put the fuse back.
Can anyone tell me what the fuse does? Can anyone help me with a wiring diagram? I read threads here that suggest the Haynes diagram is not much good. Any advice would be most welcome.
Jez