At the beginning of the war the government thought the Germans would be using gas against us so everyone was issued with a gas mask. Lampposts and letterboxes were all painted with coloured rings round them. If the rings changed colour you had 10 seconds to get your gas mask on because there was gas in the air.
During training one of the worst things was mustard gas, you had to get it off quickly because it would burn through to the bone and you did it by swabbing with lots of water. It was yellow in colour and not unlike mustard to look at and it was reckoned that if it ever got into the rivers it would stay there forever. They used to lock us in a shed and turn on the gas taps to see how long we could stay there before choking. The point of this was to get you used to gases.