Frederick Lindemann, known around Whitehall as "the Prof," had become notorious for brilliance mixed with disruption. At a formal dinner at Chequers on July 27, he joined Winston Churchill, Max Beaverbrook, Field Marshal Sir John Dill, General Sir James Marshall-Cornwall, and others. Churchill began the meal in buoyant spirits, pressing Marshall-Cornwall about the state of his two divisions, which had escaped Dunkirk but lost much of their equipment.

Marshall-Cornwall pleased Churchill at first by saying he was trying to replace a defensive mindset with an offensive one, summed up by the slogan "Hitting, not Sitting." But when Churchill asked if the corps was ready for the field, Marshall-Cornwall answered that it was far from ready because re-equipment was incomplete and training would still take months. Churchill then produced Lindemann's new readiness charts, which appeared to show the divisions largely equipped, and read the figures aloud. Marshall-Cornwall corrected him, explaining that the numbers likely counted weapons sitting in ordnance depots, not weapons actually delivered to his troops.

The contradiction exposed how Lindemann's statistics could mislead Churchill. Furious, Churchill threw the papers toward Dill and ordered him to have them checked by the next day. To shift the mood, Churchill then asked Lindemann what he had to report, and Lindemann theatrically pulled a Mills bomb from his pocket. He denounced the standard British grenade as inefficient and presented his own simplified design with a larger bursting charge. Churchill, attracted to novel weapons and quick solutions, immediately ordered Dill to scrap the Mills bomb and introduce the Lindemann grenade instead.

Dill was stunned because the army had already arranged for millions of Mills bombs to be manufactured in Britain and America. Although Churchill tried to act at once, a calmer review evidently followed later, since the Mills bomb remained in service for decades. The dinner ended on a lighter note when Churchill turned to Beaverbrook, who mocked the Prof's obsession with figures by phoning for fresh numbers and returning to announce, mischievously, that Hurricane production had risen by fifty percent in the previous forty-eight hours.