Originally Posted by
GCRyder
I suspect the question has people confused, since you say you already have the lever off. Ordinarily, the clamp is tightened and loosened by the same bolt that attaches the lever. By the time the lever comes off, the clamp is flopping around on the bar and slips off easily. If yours is not like that, it might help to post a photo.
It was that in the end, undoing the lever bolt did loosen the clamp, but not enough to make it obvious. Took a little bit of grease (elbow and the gunky stuff) to get it moving, but slipped off ok in the end.