My wife was in the Observer Corps in the 80s and allocated to a government bunker in Dundee. She became very adept at writing backwards on glass screens. After six months she was promoted to meteorological officer - partly because she had a geography O Grade and partly because she wore a short skirt to climb the ladder up to the hatch in the roof to observe the weather. She even kept the card she had to show to police in an emergency that would see her get a police escort to the bunker. They ran numerous exercises where they role-played an attack and tried to get civilians to the shelters but never managed to get above 20% success rates. One official said in reality they wouldn't give the public any warning because all it would achieve was panic stricken crowds blocking the routes to the bunker for the VIPs.