| Yep, 32mm socket is the chap you'll need. You will notice though that the nut is not very wide, so if you're better off with a plain hex socket (not one of those multi faceted socket - whatever they're called) so that the flats of the socket fit exactly on the nut.
If you can find a socket that either has no chamfering on it's faces, or only a minimal amount, it'll fit better. Because the nut is not very wide, if you think about it, a fair percentage of the socket won't actually fit, because the chamfered face of each socket flat means it will be oversized. Basically, this means that the socket can slip off the nut more easily when you're trying to torque it up. | 
Jools
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