Guess I didn't explain it well enough.
What I meant was:Hold the brass plug steady and remove the caliper from the plug by unscrewing it....
It's late,I'll take the pills and retire to bed.
Le Singe....the top of the plug is flush with the caliper body.....plus I did try all sorts of variations of twisting and turning.
I got to the point where the brass started distorting around the slot, even with the screwdriver tip spot-on the same size and width as the slot......achieving nmore torque on the screwdriver won't do more than lose me the slot altogether sadly.
Fanum,
Used to have same problem with Jap trail/motocross bikes, usually end up drilling this plug out, then drill the caliper pin and put an "R" clip in on the inside of the caliper.
Makes life easier when cleaning calipers out and replacing pads next time
Bugger me. The first time I've been useful in my life. I think I better go and lie down....
Can't really help any further. My "caps" were steel, but just very stuck. Loads of WD40, heat and skimmed knuckles did it eventually. Still mangeled the "slot" though I invested in a large tim of copper grease which is still 85% full!