Mention has been made elsewhere of the unprotected state of the Grand Fleet bases against submarine attack in the early part of the War. The matter was one of supreme importance, and formed the subject of very urgent representations to the Admiralty. Many brains were at work on the problem at the Admiralty, at the bases, and in the Fleet itself. The first step was that taken under the direction of Captain Donald S. Munro, the King’s Harbour Master at Cromarty, who devised a system of submarine obstruction which later formed the pattern for the deep-water obstructions at most of our naval bases. Owing to his energy and driving power, the entrance to Cromarty was rendered fairly secure by October 26th, 1914. Whilst he was working out a defence for Cromarty another officer, Lieutenant Bircham, R.N.V.R., under the command of Admiral Sir Robert Lowry, the Commander-in-Chief of the coast of Scotland, suggested a method for providing an obstruction for the Rosyth base. This was fitted in place by the end of October, 1914, and was also entirely successful. As soon as the Cromarty scheme was in train, I requested that obstructions on similar lines should be fitted to the three main entrances to Scapa Flow, the Hoxa entrance (by far the most likely to be attempted) being taken in hand first. Exasperating delays in the supply of the necessary material were experienced, and the first line of obstructions in the Hoxa entrance was not completed until December 29th, 1914, the first line in Switha Sound by January 12th, 1915, and that in Hoy Sound by February 19th, 1915. Meanwhile officers and men of the Fleet had improvised obstructions, first at Lough Swilly and Loch na Keal, and later at Scapa Flow, which, while not giving thorough security against a determined attempt at entry, had a psychological value. These obstructions, which were kept in existence even after the completion of the more efficient methods of dealing with the problem, involved much labour.