Added to this there was the possibility of being fired upon by the batteries at Churst and Fort Edward, guarding the narrow channel leading to the tidal estuary on the banks of which Wagshot Air Station stands. Although the forts had been warned that the two R.A.F. motor-boats were passing, there was always a chance that a highly-strung battery-commander might mistake the two grey hulls for the conning-towers of a pair of U-boats and give the order to open fire. Such a thing had been done before, with disastrous results. Suddenly Derek's reveries were broken by the coxswain shouting: "There it is, sir; a couple of points on the port bow!" Unable to comprehend the nature of the intelligence, Derek peered ahead in the direction indicated, quite expecting to see a horned mine a few yards from the bows. Then he heaved a sigh of relief, for looming faintly through the mist was the unmistakable outline of Thorbury Head. CHAPTER XXII A Mouldy Station Ten minutes later the boats were in the turmoil of the troubled water caused by the swirl of the tide over Thorbury Ledge. Had it been light enough for anyone standing on the headland to watch the two diminutive craft struggling through the broken water, he would doubtless have expected to see the frail cockle-shells founder under his eyes. It was hazardous work, certainly; but by this time Derek had the utmost confidence in the seaworthiness of his two craft. Often hidden from each other by the intervening crests, the boats behaved wondrously; but the youthful officer in charge was relieved to know that wind and tide were in the same direction. Had it been otherwise things might have been different. From the headland it was now plain sailing, for in the gathering light the slender tower of the lighthouse at Fort Churst could be discerned, standing out clearly against the dark background of the well-wooded hills. In forty minutes both boats were passing through the narrow channel. Signals were exchanged with the batteries, and the welcome order to proceed was received. It was now comparatively smooth water. The crews, recovering from their malady, were able to sit up and take nourishment in the shape of bread and bully beef. More, they began to take a lively interest in their surroundings, although the aspect of that land-locked stretch of water in war-time and in November was far different from what it had been previous to August, 1914, when the sea was dotted with the sails of countless yachts. "Wonder if it will ever be the same again?" thought Derek. "One thing's fairly certain: we won't see the German Emperor afloat here, unless as a prisoner of war on a British battleship."