The result is an anomaly that might well become serious if we had to depend upon our road system under the threat of invasion. Look, for instance, at the two great handicaps, the Humber and the Thames. A force standing up to meet a threatened landing which might be directed against Kent or against East Anglia would be divided into two sections, deprived of road communication save round through London. During the War a temporary bridge was thrown across the Thames (in the neighbourhood of Tilbury, if I remember aright), but, of course, with a gate for traffic. In normal times you could not have such a thing. The water traffic is too great and too confused. But what you could have would be a tunnel, and though the necessity for it may never arise it is also true that should it arise we shall bitterly regret not having driven that tunnel. The same remark applies with even greater force to the Humber. An attempted landing on the north-east coast of England, threatening alternatively the Lincolnshire and Yorkshire coasts, would find the defending force cut in two, and were the strategics of this position to become acute we should regret the lack of a road tunnel under the Humber, just as we should regret the lack of a road tunnel under the Thames. The third principal case, that of the Severn, is partially met by a railway tunnel--the Severn Tunnel, far below Gloucester. A road tunnel would hardly suggest itself here. There is not a sufficient “potential” for it on either side of the stream. But here again it might well happen that under the particular circumstances of war we should regret the absence of it. This negative factor, the absence of a strategic “driving motive,” has also left the windings of the internal road system at the mercy of the easiest crossings of the rivers, and we see how different the thing would have been under a strategic scheme. Consider the Roman contrast. The Roman roads of Britain were principally military. The whole scheme of Roman government was military, and the life of all that civilization was founded on the army. With the marching of men rapidly and easily from place to place as the main motive of the builders, the roads follow those great straight lines which, while duly seeking a formula of minimum effort, never sacrificed to it directness of plan. As we have seen, even at the great estuaries Roman engineers preferred a supplementary ferry to continue the road rather than deflecting it round by the first bridge.