The “departure” organisation was carefully worked out by my Staff and very minutely described in the Grand Fleet orders. It was most useful, the whole Fleet, comprising frequently 50 or more battleships, cruisers and light cruisers, and as many as 50 destroyers, being in daylight under weigh in one hour, and clear of the harbour in an hour and a half after the signal was made to proceed; on dark nights this time was lengthened by half an hour. When returning to Scapa Flow, the usual practice was for the time of entry to be arranged so that the leading squadrons passed the Pentland Skerries shortly before dawn, in order to minimise the danger from submarine attack; but it was not, of course, always possible to arrange the time of entry in this manner. In returning to Scapa, when the arrival was thus timed for dawn, the different squadrons were disposed, as a rule, in two separate lines, the lines being some five miles apart and the squadrons in each line having an interval of about three miles between them. One line would enter the Pentland Firth by passing north of the Pentland Skerries and the other by passing south of these rocks, the object being to confuse any enemy submarines that might be watching the approaches, and also to get the Fleet into the Firth as quickly as possible, as once in the tideway there was little to fear from submarine attack. If the Fleet entered Scapa Flow during darkness, the ships anchored in the centre of the Flow in certain specified berths, and waited for daylight before taking up their berths in the Fleet anchorage; towards the end of my period of command, however, coloured lights were arranged to be placed as leading-marks for the Fleet anchorage, so that ships could proceed to their final berths under all conditions. As regards mines, an exploratory search of the channel intended to be used was always carried out, if time permitted, before the Fleet left, and similarly before it returned. Three channels were used, each some 7 to 10 miles in width--one passing up the east side of the Orkneys, one running to the eastward from the Pentland Skerries, and one passing down the Scottish coast for a short distance and then to the eastward. Usually the second of these channels was used. The principal difficulty with which we had to deal when leaving or returning was fog. In a really dense fog there was great risk in attempting to leave Scapa with a large fleet, owing to the strong tides to be encountered in the Pentland Firth, and nothing but the gravest emergency would have justified the attempt being made. If it became really necessary, an organisation had been provided to meet the case, and the attempt would have been made. The interval between the various squadrons would have been considerably greater, and the time occupied in leaving would have been correspondingly increased.