how long for a 301 redirect to 'work'?

still showing in G a year on

[tomtomclub]

We put a 301 redirect on our .com domain (pointing to .co.uk) a year ago but google had already crawled the .com site when we did it.

Now, a year later when I search for domain.com I still get the old snippet from feb 2004 although it does of course redirect to .co.uk when you click on it. Is this normal or is this seen as duplicate content by google and should we permanently remove the .com site from google using the manual facility?

anj