<<When the RAF got their first Tristars from BA, the aircraft were Cat 3 capable but I believe the RAF did not train the pilots or maintain the aircraft to keep Cat 3 certification.
I am not sure of the current situation regarding the RAF and Cat 3.>>
Many, many years ago at Heathrow we were severely clamped out one evening with no civil traffic flying - before the days of CAT III. An RAF VC-10 had flown in a VIP earlier in the day and called for start-up to return to his base (Brize I think). RVR was about 50m so I asked him what was his minima for take off. He rather sniffily said: "I don't have a minima"... taxied out and took off! Nothing else moved the rest of that day/night.