Late on Friday, May 9, Hitler stayed awake at the Berghof and kept his guests with him through another of his restless, rambling nights. With top figures such as Rudolf Hess, Heinrich Himmler, Hermann Gring, and Joseph Goebbels absent, Martin Bormann saw an opening to strengthen his influence. Around two in the morning, Bormann and Hitler’s pilot, Hans Baur, pressed Hitler to answer recent RAF raids on Germany with a major attack on London, arguing that Germany needed to save face and that such a raid would also help disguise preparations for the invasion of Russia.

Hitler initially resisted because he wanted Germany’s strength concentrated on the coming eastern campaign, but the pressure worked. By dawn he was furious, and at eight o’clock Saturday morning he telephoned Luftwaffe chief of staff Hans Jeschonnek and ordered a reprisal raid on London using every aircraft available. The decision marked a direct escalation and set in motion an attack that British defenses would soon begin to anticipate.

At Ditchley, Clementine Churchill was deeply uneasy about Mary Churchill’s engagement to Eric Duncannon. She wrote privately to Max Beaverbrook that the engagement had happened with "stunning rapidity," that Winston had agreed the couple must wait six months, and that Mary was too young and had been carried away by excitement. Mary then encountered Beaverbrook by chance and later received him more warmly by telephone. Pamela, visiting from Cherkley, brought Mary two brooches and warned her not to marry a man simply because he wanted to marry her, but because she herself wanted the marriage; Mary brushed off the advice at first, though it stayed with her.

Later that day, General McNaughton and his wife hosted a small party for Mary and Eric, where guests toasted both the couple and Winston Churchill on the first anniversary of his becoming prime minister. The occasion made Mary reflect on the emotional moment of her father’s rise to office a year earlier. But after a long private talk with Eric, Mary felt her certainty beginning to weaken, showing that the engagement was already under strain.

That afternoon, RAF No. 80 Wing detected that German navigational beams had been activated, a strong sign that a raid would come that night. The RAF tracked the beam vectors, warned the filter room, and designated the evening a fighter night over London, adjusting air-defense and anti-aircraft arrangements accordingly. At 5:15 p.m., an officer warned the London fire service that "the beam is on London"; the beam, transmitted from Cherbourg, was code-named Anton, and within minutes the deputy chief sought authorization to mass one thousand fire engines in the capital.