P38A brake carrier tool?

So what is it I need to get the brake caliper carrier off? I can get the caliper off easy enough but what is the name of the star style nut and what size do I need I don't really want to buy a set if I'll only use 1

Cheers

9/16th 12 pointed ring spanner

Would it not be metric?

Mine take a 1/2" twelve pointer. The metric equivalent does fit but the imperial version is tighter. As it's a splined head rather than a hex a tight fit is better so it doesn't round the head of the bolt off.
Edit - sorry - thinking about the wrong car - I was thinking about the Defender/ The range Rover probably is 9/16 ths. The point about imperial sizes being a better fit still holds true though.

14mm is a tighter fit than 9/16ths, bolts are bihex

Depends if it's front or rear. Front are 19 mm or 3/4 AF bihex.

Going to do both both sets of disc as they are showing their age in the near future might as well buy a set