On Sunday, 15 September 1940, Winston Churchill drove from Chequers to Uxbridge, to the headquarters of the RAF’s No. 11 Fighter Group. Its 25 squadrons covered Essex, Kent, Sussex and Hampshire, and every approach across them to London. The weather, he judged, suited the enemy. He and his wife were taken down to the bomb-proof operations room, fifty feet below ground.
The room, he wrote later, was like a small theatre. Below the gallery, plotters stood around a large map table, pushing discs to show each wave of attack. Opposite, covering the entire wall where a curtain would be, was a gigantic blackboard fitted with electric bulbs. It had six columns, one for each fighter station, and a sub-column for each of their squadrons. The rows were states. The bottom row lit up for squadrons “Standing By” at two minutes’ notice. Above it came “Readiness” at five minutes, “Available” at twenty, then taken off, enemy sighted, in action, shown in red, and at the top, returning home.
“I don’t know,” said the group’s commander, Air Vice-Marshal Keith Park, as they went down, “whether anything will happen to-day.” After a quarter of an hour the plotters began to move. “40 plus” was reported from the Dieppe area, then “60 plus,” even “80 plus.” The bulbs along the bottom of the board began to glow, and soon the rising lights showed squadrons going up.
Presently the red bulbs showed that most of the squadrons were fighting. A young officer beside Churchill turned Park’s directions into orders in a calm, low monotone. Then, Churchill wrote, “All were in the air. The lower line of bulbs was out. There was not one squadron left in reserve.” Park asked headquarters for three squadrons from the neighbouring group, and they were soon absorbed too. One of the group’s aims, Churchill noted, was not to have too many squadrons on the ground refuelling at the same time, where fresh raiders could catch them.
Churchill, who had watched in silence, asked, “What other reserves have we?”
“There are none,” said Park.
No new attack came. The discs on the table began to drift east, and within minutes the action was over. As they left, Park told him that in the last twenty minutes they had been “so choked with information that we couldn’t handle it,” and that their resources had been “strained far beyond their limits.”
That evening Churchill was told the RAF had shot down 183 aircraft. Post-war records, he later wrote, put the German losses that day at 56. He still took 15 September as the crux of the Battle of Britain.