Enigma

the war memorial, braked to avoid skidding on the ice, and turned left into Wilton Avenue.
    He was panting with exertion by the time he reached the Hut, fifteen minutes later, so much so he could barely blurt out his discovery and catch his breath and stop himself from laughing at the same time:'—They're—using—it—as—a—three-rotor—machine—they're—leaving—the—fourth—rotor—in—neutral—when—they—do—the—weather—stuff—the—silly—bloody—buggers -'
    His arrival caused a commotion. The night shift all stopped working and gathered in a concerned half-circle round him—he remembered Logie, Kingcome, Puck and Proudfoot—and it was clear from their expressions they thought he really had gone mad. They sat him down and gave him a mug of tea and told him to take it again, slowly, from the beginning.
    He went through it once more, step by step, suddenly anxious there might be a flaw in his logic. Four-rotor Enigmas were restricted to U-boats and Sainte-Assise: correct? Correct. Therefore, coastal stations could only decipher three-rotor Enigma messages: correct? Pause. Correct. Therefore, when the U-boats sent their weather reports, the wireless operators must logically disengage the fourth rotor, probably by setting it at zero.
    After that, everything happened quickly. Puck ran along the corridor to the Big Room and laid out the best of the weather cribs on one of the trestle tables. By 4 A.M. they had a menu for the bombes. By breakfast one of the bombe bays was reporting a drop and Puck ran through the canteen like a schoolboy shouting: 'It's out! It's out!'
    It was the stuff of legend.
    At midday Logie telephoned the Admiralty and told the Submarine Tracking Room to stand by. Two hours later, they broke the Shark traffic for the previous Monday and the Teleprincesses, the gorgeous girls in the Teleprinter Room, began sending the translated decrypts down the line to London. They were indeed the crown jewels. Messages to raise the hairs on the back of your neck.

    FROM: U-BOAT TO CAPTAIN SCHRODER

    FORCED TO SUBMERGE BY DESTROYERS. NO CONTACT. LAST POSITION OF ENEMY AT 0815 NAVAL GRID SQUARE 1849.
    COURSE 45 DEGREES, SPEED 9 KNOTS.

    FROM: GILADORNE

    HAVE ATTACKED. CORRECT POSITION OF CONVOY IS AK1984. 050 DEGREES. AM RELOADING AND KEEPING CONTACT.

    FROM: HAUSE

    AT 0115 IN SQUARE 3969 ATTACKED, FLARES AND GUNFIRE, DIVED, DEPTH CHARGES. NO DAMAGE. AM IN NAVAL GRID SQUARE AJ3996. ALL TIN FISH, 70 CBM.

    FROM: FLAG OFFICER, U-BOATS
    TO: 'DRAUFGANGER' WOLF PACK

    TOMORROW AT 1700 BE IN NEW PATROL LINE FROM NAVAL GRID SQUARE AK2564 TO 2994. OPERATIONS AGAINST EASTBOUND CONVOY WHICH AT 1200/7/12 WAS IN NAVAL GRID SQUARE AK4189. COURSE 050 TO 070
    DEGREES. SPEED APPROX 8 KNOTS.

    By midnight they had broken, translated and teleprintered to London ninety-two Shark signals giving the Admiralty the approximate whereabouts and tactics of half the Germans' U-boat fleet.
    Jericho was in the Bombe Hut when Logie found him. He had been chasing about for the best part of nine hours and now he was supervising a changeover on one of the machines, still wearing his pyjamas under his overcoat, to the great amusement of the Wrens who tended the bombe. Logie clasped Jericho's hand in both of his and shook it vigorously.
    'The Prime Minister!' he shouted in Jericho's ear, above the clattering of the bombes.
    'What?'
    'The Prime Minister has just been on the telephone with his congratulations!'
    Logie's voice seemed a long way away. Jericho bent forward to hear better what Churchill had said and then the concrete floor melted beneath his feet and he was pitching forward into darkness.
    'Is,'said Jericho.
    'What, old thing?'
    'Just now, you said Shark was a monster and then you said it w a monster.' He pointed the fork at Logie. 'I know why you've come. You've lost it, haven't you?'
    Logie grunted and stared into the fire and Jericho felt as though someone had laid a stone on his heart. He sat back in his chair, shaking his head, then gave a snort of laughter.
    'Thank you, Tom,' said Logie, quietly. 'I'm glad you find it funny.'
    'And all the time I thought you'd come here to give me the push. That's funny. That's pretty funny, isn't it, old thing?'
    'What day is it today?' asked Logie. 'Friday.'
    'Right, right.' Logie extinguished his pipe with his thumb and stuffed it into his pocket. He sighed. 'Let me see. That means it must have happened on Monday. No, Tuesday. Sorry. We haven't had a lot of sleep