To add to the confusion caused by the bombing of London, where the Luftwaffe had tried out its new 3,600-lb high-explosive bomb, the Joint Intelligence Committee decided that a German invasion was imminent; 'a significant item of intelligence' contributing to this notion was that four Germans had been found landing by rowing boat, and had confessed that they were going to report troop movements.

The Combined Intelligence Committee, and the Joint Intelligence Committee to which they reported, had a high opinion of the speed and efficiency of the men in the rowing boat, for they chose not to use Invasion Alert No. 3 (an attack is probable within three days) or No. 2 (an attack is probable within two days). They stampeded the Chiefs of Staff into issuing Invasion Alert No. 1 attack is imminent.

Red-faced, the authorities later blamed the troops under their command for taking the warning too seriously. Special scorn was reserved for Home Guard commanders who ordered the church bells to be rung, for this was a signal that enemy parachutists were descending in the neighbourhood.

Churchill and the official historian wrote that the invasion warning was justified on the strength of the information available. But, apart from the continued buildup of barges in the Channel ports, two understrength Geschwader transferred from Air Fleet 5, and the wretched men in the rowing boat, they provided none. It became expedient to say that the No. 1 Alert was the only invasion alert available, and that what the Chiefs of Staff wanted to do was to warn the troops in south-east England that there was a good chance of an attack by seaborne German forces in the next few days. Why this announcement could not have been sent by phone, teleprinter, messengers, by means of a conference, or even broadcast over the BBC was never explained.

However, impeded only slightly by the Chiefs of Staff, London continued to attend to the damage done by its first real bombing raid. The afternoon raids continued and more bombers came that night. In London's Surrey Docks the bombs set fire to 250 acres of timber. Warehouses of paint and rum blazed. Pepper caught fire and tormented the eyes of the Civil Defence workers. "Send all the pumps you've got," said one Fire Officer, 'the whole bloody world's on fire."

Circling the burning city in his personal Hurricane, code-lettered OKI, Air Vice-Marshal Park prayed that it meant a respite for his vital sector airfields.

But bombing by daylight provided an accuracy that night bombing never could. Park was determined that the Germans should not repeat their daylight success on London. For the next big raid, he placed his squadrons well forward, to intercept a two-pronged attack that came towards London from Dover and Beachy Head. The former was intercepted skilfully enough for the Germans to bomb Canterbury instead. The southern raid was deflected from the docks the prime German target- and in bitter fighting over south-west London, bombs were scattered in city and countryside.

But again Leigh-Mallory failed to protect Park's airfields north of London. Instead his squadrons came south, to join in the air battles south-west of London.

Leigh-Mallory's determination to send his squadrons down south into 11 Group is made more puzzling by the 'territorial' attitude he took about his own Group. There was an incident in which a lone raider flew along the Group boundary being chased, by fighters of both 11 Group and 12 Group. One of Park's fighters shot it down, but it fell just inside 12 Group area. Within minutes a signal from Leigh-Mallory arrived at the desk of the 11 Group Controller: "Full explanation required why 11 Group fighters have shot down enemy aircraft into 12 Group area." >From some commanders such a signal might have contained a measure of wry humour but Leigh-Mallory did not joke about such things.

Park's handling of the fighting of 9 September was as brilliant as any in the war. Virtually none of the German bombers achieved hits on its primary target.

By now the summer had gone and the weather deteriorated rapidly. Several times the daylight raids stole in unseen over the weather. Unintercepted, the German crews went home trying to believe their Intelligence Officers, who kept repeating that RAF Fighter Command had virtually ceased to exist. When, on the next raid, they saw huge formations rising to meet them, they were disillusioned again. "Here they come," said one German flyer bitterly, 'the last fifty Spitfires."

It was the week ending 13 September that saw the RAF storage units down to the lowest point in the battle. Only eighty Hurricanes and forty-seven Spitfires were available. Although it would be unwise to place much emphasis upon this timing, it is certainly an indication of the skill with which Park and Dowding had fed aircraft into the battle.

Both sides had learned a great deal. At last German Signals had realized that the south-coast radar stations, difficult to destroy by bombing, could be nullified by radio interference. Some experts said the Germans would save their intensive jamming to coincide with the invasion.

Today came the climax of the daylight battles. Warning had come when the monitoring service heard intense radio activity from aircraft being tested and prepared for operations. And there was warning too from other sorts of radio activity by the Luftwaffe Air Fleets. From these various sources, collectively known as the Y service, it became evident that today's attack would come in two waves. Park knew that he would have to get his squadrons refuelled and replenished in record time, to engage the follow-up attack. The ground crews did not let him down.

The Luftwaffe was still experimenting with changes in formations. Today these were more complex and flew higher, having discovered that high-flying formations sometimes escaped without interception. (The radar was ineffective above 20,000 feet but the Germans did not know this for certain.) Both the height and the complexity of the forming-up gave Park a little extra time to position his defences. He had his squadrons well forward and fought the raids all the way to London, and all the way back again. The extra time gave him a chance to use his squadrons in pairs (usually from the same airfield), which he had always preferred but seldom had time to do.

Leigh-Mallory, on the other hand, persisted in using bigger and bigger big wings. Ignoring his orders, and failing to play a part in Dowding's whole strategy, Leigh-Mallory let his flyers fly south as far as London, and even beyond, leaving London completely undefended from the north.

And yet this day's fighting provided a vivid example of how impractical the big-wing operations were. Johnny Kent was flying with 303 (Polish) Squadron behind 229 Squadron. Over Croydon he sighted a large enemy formation approaching from the south. His aircraft had no common radio band with the other squadron, which was by now on a heading away from the enemy. Kent tried to call the ground Controller so that he could tell 229 about the 'bandits' but the high-frequency radios in use at this time were very poor, seldom ranging more than 40 miles. Kent's speech broke up and the Controller could not understand.

So as the other squadron moved away, Kent sent nine of his Hurricanes to attack the bombers while he led the remaining two in an attack on the fifty fighters. By that time, 303 Squadron had lost its initial advantage and the Germans were already bombing.

Kent was never an advocate of the big-wing theories but he shared some of the proponents" criticisms of the Controllers. On another occasion, vectored towards a dangerous-looking thundercloud, Kent, an ex-test pilot and one of the most capable aviators flying in the Battle, asked for another course. The Controller became angry, but not as angry as Kent did when he found himself in the middle of the London balloon barrage, having lost radio contact with the Controller. When eventually Kent regained radio contact he was told, "Bandit ten miles ahead of you."