The possibility of war remains, however, and I wish in conclusion to emphasize the fact that in my belief the security of this country in the event of war will depend upon our strength in the air. The development of the offensive powers of aviation have already destroyed "the silver streak" on which we relied in the past. When we remember that it is less than twenty years since the first successful aeroplane was flown, when we recall the almost miraculous development of the fighting powers of aircraft during the four and a half years of war, and also the further developments which were on the point of being utilized when the war ended, it seems certain that from the point of view of war Britain has ceased to be an island. The "silver streak" would have been little protection but for our naval supremacy, and in the future our security will depend as much upon superiority in the air as it has depended in the past upon our superiority at sea. And this superiority in the air can only be attained in the same way in which we secured our supremacy at sea. That supremacy was not really gained by developing great navies. It was gained by our mercantile marine, which made the great navies possible. Our future security can only be gained by the development of commercial aviation. _Printed in Great Britain by_ Butler & Tanner, _Frome and London_. Transcriber's Endnotes: Variant spellings, e.g. _Frankfort_ and _Frankfurt_, remain as printed. Significant amendments have been listed below: Page 67, 'Poperighe' amended to _Poperinghe_. Page 117, 'Junker' amended to _Junkers_.