If, when war began, anyone in Britain's air defences believed that the system was functioning well, the events of 6 September should have changed their mind. According to Dowding it all began when a "refugee aircraft from Holland" was reported. Since there had been no notification of this incoming flight, RAF fighters were sent to intercept.

Like the aerial of any cheap transistor radio, the radar aerials produced a strong signal when at right angles to the aircraft (or radio station). Only by electrical screening could the radar distinguish seaward aircraft from those behind the aerials. On 6 September the screening failed, said Dowding, and the fighters sent up from British airfields to intercept appeared on the screens as blips out to sea. More RAF fighters took to the air, and each one looked like another incoming raider.

How the fighting began is still unknown but as the Spitfires from Hornchurch met the Hurricanes from North Weald, a battle began and two Hurricanes were shot down. One pilot died.

At Dowding's HQ the movements of the coloured counters were being watched by King George VI, who had chosen that day to pay a visit. "I fear I was a most distrait host," said Dowding, who realized that something had gone terribly wrong.

The 'sense-finding screen' at Canewdon was checked and found to be working perfectly. Afterwards Watson-Watt insisted that all the fighters had been seawards of the aerials and the radar had reported accurately.

The rights and wrongs were never settled but there began an urgent reassessment of the radar and reporting network. Electronic sets that would enable RAF aircraft to identify themselves were ordered immediately. These IFF sets were crude and imperfect devices but, in September, 500 of them were put together by hand, so that the fighters could have them. And from the fiasco came an instruction that enemy raids should be confirmed by a visual sighting by the Observer Corps, before the fighters went in. As we shall see, this rule brought new difficulties.

Meanwhile the Luftwaffe were busy elsewhere, providing intensive air bombardment for the German army invading Poland. There was little air fighting, for the Polish air force had been almost destroyed by attacks upon the airfields. While the fighting continued, the governments of Britain and France worked hard at the task of convincing themselves that the Luftwaffe would not attack western cities unless provoked to it. The Anglo-French air forces were forbidden to drop anything more lethal than propaganda leaflets over German towns. RAF Bomber Command was allowed across the North Sea with bombs but only to attack German warships. Trying this in daylight, without fighter escort, they suffered heavy casualties. As 1939 came to an end RAF Bomber Command's operations had proved disastrous. The raids had suffered a loss rate of 9.5 per cent (never again, in any year of the war, did losses reach even half this rate). Instead of adding fighter escort to their raids, they simply abandoned daylight bombing, which had been the basis of all their pre-war planning.

At night, the RAF contented themselves with leaflet dropping, and few of the attacking airmen ever found the designated targets. Replying to a proposal that the German forests could be set afire with incendiary bombs, Sir Kingsley Wood, Britain's Air Minister, a one-time insurance consultant, revealed the official attitude: "Are you aware it is private property? Why, you will be asking me to bomb Essen next."

On 10 May 1940, lacking such respect for property, panzer groups crossed the frontier without customs formalities. They were heading for the Meuse. The great blitzkrieg of 1940 had begun. The French asked the British to employ their heavy bomber force against the German columns. By 15 May panzer forces had bridged the Meuse. At a meeting of the War Cabinet on that day it was agreed that RAF Bomber Command should be authorized to attack.

In accord with the same theories that so impressed Göring, the RAF mounted the largest air bombardment the world had yet seen, and sent it off that same night. It was not sent to attack the bridges on the Meuse. Complete reasonings of strategy and the influence of Douhet selected oil industry targets in the densely populated Ruhr, an under cover of darkness 100 Whitley, Hampden, and Wellington bombers tried to find them.

The French had argued desperately that air attack upon the Ruhr could have no effect upon Guderian's armoured invasion of France. The French were entirely right. The RAF official history admits that the bombers "achieved none of their objects. Industrial damage was negligible," and goes on to explain that the greatest benefit expected from this opening shot of the strategic bombing of Germany was "an informal invitation to the Luftwaffe to bomb London." By this means it was hoped to divert the German air offensive away from the French ground force: To what extent this motive was arrived at, after the raid failed to be anything better than a provocation, can only be guessed.

That particular War Cabinet meeting on 15 May was as important as any in the nation's history. Dowding, alarmed by the numbers of his precious Hurricane fighters being sent to fight in France, had asked for permission to talk to the Cabinet. To his surprise he was invited along.

It is important to record the nature of Dowding's objection. His upbringing, training, and his character would forbid his commenting upon the strategic advisability of moving fighter aircraft to France. Such a decision would, rightly, be that of the War Cabinet, advised by the Air Ministry. Dowding argued that, since the Air Ministry had long since decided that 52 squadrons would be needed for the defence of Britain, fighters sent to France must be written off as an overseas force, and separated from home defence. The force remaining in Britain must then be expanded to 52 squadrons.

Technically Dowding never argued his case before the Cabinet, and for entirely new information throwing light on this mysterious incident I am indebted to Professor A. J. P. Taylor who has most generously passed his research to me.

Dowding argued his case to Churchill, Archibald Sinclair (the new Air Minister), Beaverbrook (newly appointed Minister of Aircraft Production), and Sir Cyril Newall (Chief of Air Staff). He told them his 52 squadrons were already reduced to 36 and that at the present rate that Hurricanes were being shot down in France, there would be none left anywhere within two weeks. He produced a graph to support this contention and placed it in front of Churchill.

Dowding stayed on for the subsequent Cabinet meeting (it was not unusual for the room to be crowded with people in spite of its small permanent complement). However, Dowding didn't speak before the Cabinet, neither did anyone else refer to Dowding's plea. After the Cabinet meeting, Newall insisted that Sinclair should have raised the matter but by then it was too late. Orders were given that four more fighter squadrons should be sent to France. Dowding went back to Fighter Command HQ and described the situation just as he had put it to Churchill in an official letter to the Under Secretary of State for Air. It proved a sound precaution, as we shall see.

The next day, 16 May, Churchill flew to Paris to hear Paul Reynaud, the French Premier, plead for still more RAF fighters to stem the German flood. Churchill phoned London (using two officers speaking Hindustani to preserve secrecy) and asked the Cabinet to agree that another six squadrons should be sent to France (additional to the four taken from Dowding on the previous day). The Cabinet met late that evening to consider it. Without Churchill's commanding presence they wavered. The ineffectual Sinclair was emboldened enough to tell them about Dowding's argument. Newall added that lack of suitable French airfields was another factor. (For it must be remembered that the Hurricanes would need a complex retinue of men and a considerable amount of equipment and spares to operate from France and France was now in chaos.) Newall referred to "the figures laid before us by Air Chief Marshal Dowding yesterday," meaning not the Cabinet but the meeting beforehand. The Cabinet did not dare to defy Churchill but they compromised. They agreed that six more Hurricane squadrons could operate from French airfields, providing they returned to bases in England each night.