Rules stopped pilot's fog landing
Can't see the reason for any red faces. It's not like he had a go and cocked up an approach, he (and his possibly his first officer) weren't qualified for. Better for the passengers and the company to divert back to Cardiff than to dump them at another airport in France or England.
Rule 1: When possible divert to where your car is parked
There is also the possibility the conditions would still be out of limits for a Cat II approach as the reduction in minimas isn't huge
Cat II training is increasingly time consuming in the Sim and requires on the line training, so even at the best of times can take several months to get signed off on initially. Can't say I've had to use one in anger as of yet