Editing Battle of Britain (section)

===Intelligence===
While Luftwaffe intelligence reports underestimated British fighter forces and aircraft production, the British intelligence estimates went the other way: they overestimated German aircraft production, numbers and range of aircraft available, and numbers of Luftwaffe pilots. In action, the Luftwaffe believed from their pilot claims and the impression given by aerial reconnaissance that the RAF was close to defeat, and the British made strenuous efforts to overcome the perceived advantages held by their opponents.{{sfn|Overy|2013|pp=79–80}}

It is unclear how much the British intercepts of the [[Enigma cipher]], used for high-security German radio communications, affected the battle. [[Ultra (cryptography)|Ultra]], the information obtained from Enigma intercepts, gave the highest echelons of the British command a view of German intentions. According to [[F. W. Winterbotham]], who was the senior Air Staff representative in the Secret Intelligence Service,<ref>{{harvnb|Winterbotham|1975|p=13}}</ref> Ultra helped establish the strength and composition of the Luftwaffe's formations, the aims of the commanders<ref>{{harvnb|Winterbotham|1975|pp=61–63}}</ref> and provided early warning of some raids.<ref>{{harvnb|Winterbotham|1975|pp=68–69}}</ref> In early August it was decided that a small unit would be set up at FCHQ, which would process the flow of information from Bletchley and provide Dowding only with the most essential Ultra material; thus the Air Ministry did not have to send a continual flow of information to FCHQ, preserving secrecy, and Dowding was not inundated with non-essential information. Keith Park and his controllers were also told about Ultra.<ref>{{harvnb|Winterbotham|1975|p=65}}</ref> In a further attempt to camouflage the existence of Ultra, Dowding created a unit named [[No. 421 (Reconnaissance) Flight RAF]]. This unit (which later became [[No. 91 Squadron RAF]]), was equipped with Hurricanes and Spitfires and sent out aircraft to search for and report Luftwaffe formations approaching England.<ref>{{harvnb|Ramsay|1989|p=5}}</ref> In addition, the radio listening service (known as [[Y-stations|Y Service]]), monitoring the patterns of Luftwaffe radio traffic contributed considerably to the early warning of raids.