[C-u M-q] -> unfill-paragraph

[Tom Roche]

I'm running

$ lsb_release -ds
Linux Mint Debian Edition # Update Pack 3
$ uname -rv
2.6.39-2-amd64 #1 SMP Tue Jul 5 02:51:22 UTC 2011
$ emacs --version
GNU Emacs 23.3.1

on which M-q "runs the command fill-paragraph". Therefore ISTM
C-u M-q should run the command unfill-paragraph ... but it does not.
How to accomplish that? I tried

- (define-key global-map "\C-u\M-q" 'unfill-paragraph)

but that fails with error=

- Lisp error: (error "Key sequence C-u M-q starts with non-prefix key C-u")

Apologies if this is a FAQ: feel free to send links to RTFM.

TIA, Tom Roche <Tom_Roche@pobox.com>