The Chronology: Page-48
Saturday September 21st 1940

The day opened to scattered cloud although along the Estuary and the River Thames as far as London there was considerable haze. Once this cleared, most of the south was fine with scattered cloud but by midday cloud had started to build up. In the north there was cloud with sunny spells but it remained dry.

Early morning dawned with cloudless skies as no sign of the enemy. It was to remain that way for most of the day. Radar picked up an occasional aircraft, but these were believed to be on reconnaissance flights as they kept clear of the English coast. This was to be one of the quietest days of the battle, with more action being seen behind the scenes than in the air.

The invasion of German troops on the island of great Britain was called "Cromwell" and all stations had been placed on standby as the possibility was always there that an invasion was always a possibility. But just as the Battle of Britain in the air seemed to be slowing down, so was the possibility of any German invasion for at least this year. Now, almost into the month of October, the days would be becoming shorter, the weather would soon deteriorate with the waters of the Channel becoming rougher and the signs from the German held Channel ports indicated that Bomber Command had all but destroyed any hope of the German infantry using the ports as a dispersal point for the Channel crossing.

No hint of relaxation of alertness against the threat of invasion was allowed to percolate through to the armed forces, nor the civilian population. It was premature for that. But the view of the War Cabinet and of the most senior officers in all the Services was that with the days shortening, the weather deteriorating and the equinox approaching, it would now be most foolhardy of Hitler to attempt a crossing in 1940.

On 21st September ‘Cromwell’ was cancelled and Alert No. 2 reinstated. Anthony Eden, while relaxing one morning at Elham, was therefore all the more surprised to hear from Churchill by telephone on 22nd September that he had just received a call from the American President that, for sure, the Germans would invade that very day. Eden took a walk to the Dover cliffs. He peered down through the fog and noted an exceedingly choppy sea. He then returned home and telephoned Churchill. An invasion, he said, seemed highly unlikely, and in any case they would all be sea-sick by the time they arrived by barge.

The next day Roosevelt telephoned again, this time to apologise. ‘I’m so sorry,’ he said. ‘The codes got mixed. It was Indo-China, not England, and Japan, not Germany.’ And that, indeed, was the case.

Hough and Richards Battle of Britain A Jubilee History Hodder & Stoughton 1989 p294

But if one was to get the impression that tensions were easing, what with a day of very little combat action and "Cromwell" being cancelled. Fighter Command was in fact strengthening its commitment to battle with the introduction of 421 Flight.

One of the problems that Fighter Command encountered was the fact that when radar picked up approaching enemy aircraft and formations, it was not known as to what type of aircraft they were until clarified by spotters or the Observer Corps. With the approach of German bombers, Keith Park had just enough time to scramble his fighters, get to the correct height to attack and intercept the enemy as it crossed the coast. But with this new tactic of sending formations of Bf109s, often in Geschwader force, there was not enough time to scramble the fighters and meet them as they crossed the coast. As experienced over the last few days and on those occasions that Bf109 formations made their intended attacks on British targets, they generally would be well over the coastline and much closer to London before they were intercepted by British fighters.

It was on this day that Air Chief Marshal Hugh Dowding was to authorise the formation of a new unit that was to become known as 421 Flight. This was instigated in collaboration with Keith park because it was now felt that with Bf109 formations that could cross the Channel quicker than the bombers that they once escorted, their would be no chance of British fighters intercepting them in time once they had been positively identified.

The task of 421 Flight that was equipped with Hurricanes, was to fly in small formations on reconnaissance missions over the Channel to report on any build up and composition of these formations prior to them reaching the English coastline. This way, as well as the detection being made on radar stations along the coast of their location, 421 Flight would be vectored into a position where they could provide details back to their sector station of type and strength of the enemy much earlier than if it was left to the Observer Corps alone. Initially, the flight was formed at Gravesend in mid October and on October 31st was posted to West Malling and before the end of 1940 they had been moved to Hawkinge.

The formation of 421 Flight (which was later to become 91 Squadron) was naturally too late for the Battle of Britain. Some authorities say that such a squadron should have been formed earlier so as to provide early indications of strength and composition of the enemy. But again, this would have been another of the many debatable points that arose during the Battle of Britain.

In general, this was an exceptionally quiet day. Small nuisance raids by small formations of enemy aircraft had attacked both Kenley and Biggin Hill aerodromes but these were thwarted by fighters from Kenley, Biggin Hill and Croydon. 238 Squadron had accounted for one destroyed while the Spitfires of 602 and 611 Squadrons accounted for one each destroyed. One of the Do17s damaged by 802 Squadron managed to get back to the French coast, but was to crash land at Landerneau killing all on board.

The usual night raids continued on London and Liverpool which was now becoming a regular occurrence. Although the East End of London still came under constant bombardment, other targets in and around London were now being hit. Spasmodic raids around Tynemouth and County Durham also occurred but records indicate that no casualties were recorded.

There were no casualties on either side on this day.

The Battle of Britain - 1940 website Battle of Britain Historical Society 2007