The programme for mobilization was, in the main, successfully carried out. The headquarters of the Royal Flying Corps left Farnborough for Southampton on the night of the 11th of August, their motor transport having gone before. They embarked at Southampton, with their horses, and reached Amiens on the morning of the 13th. The movements of the Aircraft Park, though it was the last unit to leave England, may be next recorded, because it was in effect the travelling base of the squadrons. The personnel and equipment were entrained at Farnborough during the evening of Saturday, the 15th of August, and travelled to Avonmouth. Of the twenty machines allotted to them only four, all Sopwith Tabloids, were actually taken over in cases. Of the other sixteen (nine B.E. 2's, one B.E. 2 c, three B.E. 8's, and three Henri Farmans) about half were used to bring the squadrons up to establishment; the remainder were flown over to Amiens by the personnel of the Aircraft Park, or by the spare pilots who accompanied the squadrons. The Aircraft Park embarked at Avonmouth very early on the morning of the 17th, arriving at Boulogne on the night of the 18th. They disembarked, an unfamiliar apparition, on the following morning. The landing officer had no precedent to guide him in dealing with them. Wing Commander W. D. Beatty tells how a wire was dispatched to General Headquarters: 'An unnumbered unit without aeroplanes which calls itself an Aircraft Park has arrived. What are we to do with it?' If the question was not promptly answered at Boulogne it was answered later on. The original Aircraft Park was the nucleus of that vast system of supply and repair which supported the squadrons operating on the western front and kept them in fighting trim.