Air Raid Precautions
From Tardis Wiki, the free Doctor Who reference
Air Raid Precautions, or the ARP, was an organisation formed to coordinate protection and defence during the London Blitz. Nearly one in six Londoners were involved in civil defence. The ARP issued gas masks to citizens and publicised the constant need for vigilance and caution. Precautions included strict "blackout" rules, and procedures were wll established for what people should do when the sirens signalled an approaching raid. The ARP was also responsible for putting up around fifty barrage balloons. (PROSE: The Time Traveller's Almanac)
