For the next half-hour I watched him, fascinated with his sure grasp of London's intricate defences, and amazed, though I had thought I knew his capability, at the swiftness and decision with which he issued what to me seemed a veritable jumble of orders. To centre after centre of the aircraft defences he spoke a series of numbers, so bewildering in their speed and complexity that an enemy agent seated in the very room could not have gained a scrap of information. Even to me, familiar as I am with almost every branch of code work, it was a veritable revelation. "I think we are ready for them now," he said finally, wiping the perspiration from his face, and I could see that even to him the strain had been severe. How well he had done his work all England was to know the next day, though the public never even suspected the magnitude of his task. There was now nothing to do but wait; our traps were set, and it remained to be seen whether the enemy would walk into them. I made my way to my chambers for a few hours' rest and was soon deeply asleep. At half-past nine Burton, my man, roused me. "The first warning has just come in," he said. I dressed swiftly and sat down to snatch a hasty supper, knowing well that it might be many hours before I tasted another meal. It was exactly ten o'clock when the report of the first maroon broke the stillness, and London, with one accord, hastened to cover. Ten minutes later the streets were deserted, and a midnight hush reigned supreme. The great city seemed a city of the dead. As we listened a faint, distant boom struck softly on our ears. The strafe had begun! Suddenly, far away to the eastward, a searchlight flickered up into the sky; another and another followed in rapid succession, and soon the entire sky was covered and chequered by dozens of wavering pillars of flame, moving to and fro, methodically searching the heavens as though moved by a single hand. Far above us I caught the soft purr of an aeroplane, evidently one of our own, for the sound was quite different from the deeper and rougher note of the Gothas. Suddenly, with a deafening crash, half a dozen guns barked simultaneously, and, looking out, I saw far away, seemingly caught on a pencil of living light, the ethereal butterfly shape of an enemy aircraft. A second later, in quick succession, came the unmistakable sound of bursting bombs. In the midst of the tumult a single tiny light showed for a moment far up in the sky, just outside the ring of shrapnel that was bursting all round the enemy craft, now hopelessly entangled in the beams of a dozen converging searchlights, and, dive and drop as it would, utterly unable to escape from the zone of effulgent radiance in which it seemed to float.