How do I remove my Campagnolo Veloce rear brake caliper? I'm trying to remove my rear brake caliper to put a fender/mudguard clamp on. I've removed the rear nut and I assume the brake should then slide straight out. But it won't. It is definitely a little loose, it will rotate freely and has maybe 1mm of play, but even putting a reasonable amount of force on it, it will not slide out of the hole in the rear frame.

What am I missing? I assume I don't need to unscrew the caliper out of the frame.

Edit: Sorry about my woeful care of this question. I meant to put up some photos and explain in more detail, but didn't get around to it :(

In the end I unscrewed the "rear" nut (closest to the front of the bike) a little and tapped it lightly with a wrench and the caliper did come out. Turns out it was just a very tight fit. Thanks!
Seeing as you've removed the nut, you could try to insert a punch through the mounting hole, and gently tap it a few times to try and free it. I reckon there's dirt, mud, and perhaps rust in there that's causing it to stick. A picture would be useful if something else is amiss, but it's hard to imagine anything else.