This second lesson-from-history article examines this decision-making environment at Bentley Priory more closely, how it was at the center of an integrated air defense system, and part of an overall sense-and-respond system used by RAF Fighter Command.
In May 1940, Churchill, faced with an imminent invasion, ran a project that integrated four areas at different levels of development and maturity. These areas were Storey's Gate, Bletchley Park, Bentley Priory and the supply chain for fighter production run by Whitehall:
- Bletchley Park collected and deciphered encrypted enemy communications. This provided proactive intelligence on the enemy's intentions and the overall order of battle.
- Whitehall revolutionized the fighter supply chain and turned it into a demand-driven model, driven by and synchronized closely to Bentley Priory.
- Bentley Priory was the operational headquarters of RAF Fighter Command and at the center of a real-time decision-making environment developed by its leader Air Marshall Hugh Dowding. Its operations center was linked to an early-warning system and fed information to a hierarchy of Group/Sector operations centers beneath it.
- The command centre or headquarters of the whole operation was run from Storey's Gate where the map room tracked key performance indicators, e.g., from the fighter supply chain, as well as estimates of enemy fighter production. The command center presided over and issued orders to the other commands.
Collectively these four integrated areas gave Churchill a solution to respond with to an enemy threat.
Figure 1: Churchill's Four Integrated Areas Sensing
Bentley Priory aggregated information from the following sources that provided early warning of incoming raids:
- The first line of the early-warning system was Bletchley Park, which passed top-secret Ultra information to Bentley Priory. The Luftwaffe thought its encrypted communications were unbreakable. This top-grade intelligence would normally be of a highly strategic nature - the date and time of a raid, its size, the type of planes and possibly the target. It would be passed to Bentley Priory in a very secure fashion, not directly to the operations room but to a few handpicked individuals through a special liaison unit.
- The second line of the early-warning system was made up of 50 radar stations. There were two types of complementary radar stations: long and short range. The former could pick up high-flying enemy aircraft at 30,000 feet and up to 150 miles away. The latter had a shorter range, but could pick up low-flying enemy aircraft. Both operated on pattern recognition and provided information on incoming raids. With a degree of accuracy, radar information provided enemy position, direction, height, and estimated strength. Radar crews operating both in the low and high-level stations aggregated this information. The aggregated information was phoned directly to a radar operation's command rooms or headquarters. This had a filter room where sightings and detection information could be aggregated, analyzed and organized. The information was then passed by telephone onto the filter room at Bentley Priory for further processing.
- The third line of the early-warning system was made up of by the observer corps. It consisted of civilian volunteers who spotted incoming enemy aircraft through binoculars. They identified and assessed the enemy aircraft strength from 1,000 observation posts, based on the recognition of silhouettes and patterns. The corps could only track aircraft detected by the radar stations. Observer corps information was aggregated by the observer corps headquarters, which in turn was passed by telephone onto the filter room at Bentley Priory for further processing.
Together the radar stations and observer corps covered nearly ninety percent of United Kingdom's (UK) coastline.
Figure 2: Coastline Covered by Radar Stations and Observer Corps
Decision-Making
The filter room at Bentley Priory headquarters was the communications hub that aggregated all this disparate information collected from the early warning system. Occasionally there were other sources that passed new information to Bentley Priory namely, other operations centers and pilots. All this information was integrated in real time and passed directly into the operations room.
Figure 3: Operations Room at Bentley Priory, Courtesy of the Imperial War Museum, London
The Bentley Priory operations room was to have one of the most sophisticated real-time event models in the entire solution, specifically with an elegant user-interface. The purpose of the model was to map a visual representation of the skies above the UK. It was run by the Women of the Auxiliary Air Force (WAAFs). The map table used counters to show the location of friendly and enemy aircraft on a scaled map of the UK. The WAAFs would receive information from the filter room through headsets. As enemy planes took off in France, they were tracked and plotted onto this real-time model, reflecting every change. The counters on the glass-covered table were color-coded:
- A red F on white background was for friendly aircraft,
- A black X on yellow meant unidentified, and
- A black H on yellow was for hostile (representing enemy formations) aircraft.
The WAAFs changed the color of all the enemy counters every five minutes from yellow to red, and then to blue. These colors corresponded to the operations room's clock, which was also color-coded (yellow, red and blue) in five-minute increments. This gave a real-time snapshot of a raid in progress, and how it was evolving.
