Yeah +1 for the pinch bolt! Can be a right pain to remove....usually snaps and resulting in removing the full leg to drill it out!
A good idea is to remove the wheel, undo the nut, spray lots of WD40/GT85 or similar in and around, maybe a few gentle taps on the bolt and see if you can get any movement on it etc. Then do the other side. two days later repeat. and again if you can't get any movement on the bolt. Keep doing it until you get movement. tap bolt in and out. DON'T MUSHROOM THE THREAD END THOUGH!
When fitting new pinch bolt, use plenty of copper grease on it. Ensure the hollow is full of CG. This will aid you in future if you need to remove again.
My Dad got a garage to replace a top arm on his S8, labour alone came in at £450 as they snapped the pinch bolt and charged him the time it took them to remove the full leg and drill the old bolt out as they sent it away to be drilled! Shocking. Needles to say he isn't using that garage anymore!