4.11 Police Force By April 1939, it had been realised that Bristol's Police Service, then some 670 strong, would not be able to carry out single-handed all the duties which would fall upon it under war time conditions. Accordingly it was decided to augment them by enrolling an equal number of men as Police War Reserves who would be called upon to perform the duties of constables. Women were also recruited for the Woman's Auxiliary Police Corps, to assist in the administrative duties as well as undertaking some of the duties previously regarded as those of a constable. In addition, there were also available recently retired men who were members of the First Police Reserve, as well as the Special Constabulary. All these, as well as the regular officers, had to be trained in civil defence measures, and in the course of this training were closely associated with the various branches of the ARP organisation, consequently a good foundation of efficiency and understanding was laid, aided considerably by the fact that in Bristol the Chief Constable was also in executive charge of the Wardens. 4.11.1 Warning System The police also had the responsibility of sounding the air raid sirens, acting upon instructions issued by RAF Fighter Command, and for this purpose the country was divided into about 100 districts, the boundaries of which were fixed in relation to the Post Office telephone organisation. The receipt of message YELLOW, the preliminary warning, gave 22 minutes notice before aircraft could be expected overhead, and although it caused all the Civil Defence services to be put on stand-by, it was never divulged to the public. However, the arrival of action warning RED (Red Alert), giving 12 minutes advance warning of the enemy's arrival, authorised the sounding of the audible sirens on a two-minute fluctuating or warbling note of varying pitch, while the receipt of the WHITE message (All Clear) would cause the sirens to sound a continuous signal for two minutes, indicating that the enemy aircraft had passed out of the district, after which all preparations could be relaxed. NEXT