Fighter Command Headquarters at RAF Bentley Priory. The plots were assessed to determine whether they were "hostile" or "friendly". If hostile, the information was sent to the main "operations room", which was in a large underground bunker. Plotting raids Here, the course information of each raid was plotted by Women's Auxiliary Air Force (WAAF), who received information by telephone. Additional intelligence was provided by the Y Service radio posts, which monitored enemy radio communications, and the Ultra decoding centre based at Bletchley Park, which gave the RAF intelligence on the German order of battle. Colour-coded counters representing each raid were placed on a large table, which had a map of Britain overlaid and squared off with a British Modified Grid. As the plots of the raiding aircraft moved, the counters were pushed across the map by magnetic "rakes". This system enabled the main "Fighter Controller" and Dowding to see where each formation was heading, at what height, and in what strength. This allowed an estimate to be made of possible targets. The age of the information was denoted from the colour of the counter. The simplicity of the system meant that decisions could be made quickly. Communication and interception This information was simultaneously sent to the headquarters of each group, where it was cross-checked through a filter room before being sent through to another operations room, housed in an underground bunker. Because Group had tactical control of the battle, the operations room was different in layout from the main headquarters at Bentley Priory. The main map on the plotting table represented the group command area and its associated airfields. Extensive radio and telephone equipment transmitted and received a constant flow of information from the various sector airfields as well as the Observer Corps, AA Command and the navy. The "Duty fighter controller" was the Group GOC's personal representative and was tasked with controlling how and when each raid would be intercepted. If the telephone system failed engineers would be on site within minutes to repair the broken links. Battle KG 2 raid On the morning of 13 August, the weather was bad and Göring ordered a postponement of raids. However, the Dornier Do 17s of KG 2 were not informed and took off at 04:50 for their target. They were to meet with their escorts from ZG 26 over the Channel. ZG 26 received the cancellation order, but II., and