We were still flying annual 'civil defence' weeks with fire and police officers at University Air Squadrons in the 1990s - and great fun it was too. Convoy control (radio out) was the sport of kings, but the average passenger could only stand a couple of minutes before turning green and reaching for the bag...
Unfortunately some grown-up did some delving and found that the requirement had never been terminated when the rest of the CD system had been binned.
So it stopped. What a shame, I thoroughly enjoyed the licensed hooliganism of chasing round the Cotswolds navigating on a 50 thou map at 250' with various amiable coppers and firies!