Richie, I remember a case like this in the news a few months ago. I'm sure there were threads about it, if you go back through the archives.
I think it was one of the budget airlines, flying from up north somewhere to one of the London airports (my memory of the details is a little hazy!) The first officer had recently joined the company, and as such hadn't had a chance to do the company's CAT3 training yet. That wasn't considered a problem, since the forecast was good, but the forecast was wrong and CAT3 conditions existed at the destination. The aircraft diverted to the Midlands somewhere, and the airline flew in another (CAT3-trained) crew member who was then able to fly the aircraft and pax to its original intended destination.
FFF
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