From the National Archives and Records Administration

The first report came at 11.04 am: the Chain Home radar station at Dover had detected 40-plus enemy aircraft in the Calais-Boulogne area. The intelligence was filtered through Stanmore Park, Fighter Command HQ, and forwarded to Uxbridge with the designation ‘hostile’.

Within ten minutes, four  marker-blocks had been raked into position on the map-table. One represented 25 Dornier Do 17 bombers. The others were further flotillas of Messerschmitts. One would provide close escort for the bombers, another would fly extended cover, and the third was on a ‘free hunt’ for enemy fighters. Altogether, there were about 120 incoming German aircraft.

The Dorniers’ target was London, but it had been chosen because Fighter Command would have to commit its fighters to aerial combat in order to defend it. The real aim was to destroy Hurricanes and Spitfires. German intelligence was convinced that Fighter Command was haemorrhaging badly and close to collapse. If true, Operation Sealion, the invasion of Britain, might yet be launched in autumn 1940.

Air Vice-Marshal Keith Park, alongside his senior fighter controller, Wing Commander Lord Willoughby de Broke, now had to make a series of critical, close-call decisions. The enemy bombers were the target, but to get at them the enemy fighter protection would have to be stripped away. London was at the limit of the Messerschmitts’ range. If they could be drawn into high-speed aerial combat on the approach, they would consume fuel and be forced to turn for home before the Dorniers could complete their mission, leaving the German bombers unprotected against direct fighter attack.

Two squadrons were scrambled at Biggin Hill (20 Spitfires). More blocks appeared on the map-table. Ten minutes later, six more squadrons were sent up from Northolt, Kenley, and Debden (68 Hurricanes). Five minutes more, and another three squadrons were ordered up from Hornchurch (12 Spitfires) and North Weald (20 Hurricanes). At the same time, Park phoned for right flank support from 10 Group, and for cover for his northern airfields from 12 Group.

As 72 and 92 Squadrons from Biggin Hill dived on the German bombers just before noon, lights lit up on the board at Uxbridge indicating ‘engaged’. 253 and 501 Squadrons from Kenley were also closing, approaching from directly in front at the same height, aiming for a head-on attack. Soon there were more: 229 and 303 Squadrons from Northolt.

The sky above mid-Kent became a swirling mêlée of fighters closing, banking, and twisting. The first attack on the German formation by five squadrons was scrappy and indecisive. Ten minutes later, the second attack, this time by four squadrons, went in. Again, there were few kills, and the bombers kept formation and pressed on to the edge of London.

But the first two waves had done their work, drawing the enemy fighters into combat over Kent and running down their fuel. As the Messerschmitts headed for home, the Dorniers found themselves on their own as they began their bombing run over Battersea’s complex of railway choke-points.

British fighters harried the Dorniers as they ran for home. Those that broke formation and straggled, having lost their way or suffered too much damage, were easy prey for the swarms of Hurricanes and Spitfires. But 15 of the original 25 held together, protected by the defensive cross-fire of their multiple guns, and by fighters of the withdrawal escort force of Me 109s now coming into action for the first time. Six were shot down. Four others straggled but made it back to France.

The last of the raiders had passed the English coast by 12.45. The all-clear sounded. Uxbridge relaxed. The lull was brief. An hour later, the coastal radars picked up the first evidence of the second wave. As the marker-blocks stacked up on the map-table, it was soon clear this was bigger. Even so, early reports of enemy strength underestimated by half…

Pick up the first issue of Military Times to read how the ferocity and bravery of the British pilots shattered the morale of their German counterparts, and how on this day, they went on to win the Battle of Britain.