But, unless I am mistaken, the more obvious track of a passenger steamer route between the French ports and the Belgian, Dutch, and German ones does not exist save in the case of the great liners which touch at Cherbourg. A man desiring to go from Boulogne to Flushing by sea or from some lower French port to, say, Amsterdam, would very probably find his cheapest road to lie by way of going into the Thames and out of it. We must not exaggerate this element in the present position of London, where it is but a survival and that a small one: but in the past, and particularly in the establishment of the port at the end of the Dark Ages and the beginning of the Middle Ages, this ‘facing’ of London River towards the great political frontier line of Europe, was of capital importance. Scandinavia, the Baltic, Frisia, and the Dutch ports had all known their way to London for centuries when the Norman Conquest, and still more the succeeding Angevin monarchy, brought round into London River a new wealth of trade from the Seine, the Loire, and the Garonne. [Illustration: TWICKENHAM FERRY] In all that has preceded we have been considering London as the creation of the river in its civil aspect alone; it remains to consider the town and the stream in their effect upon the military history of the country, and to that I shall now turn. FOOTNOTE: [4] The reader may see quoted in full in Sir Laurence Gomme’s _The Governance of London_ (p. 346) the precedents upon which Coke founded his opinion in 1597, including the verdict of 29 Ed. I., concerning in particular the portage of salt upon the Thames. “Quod nullus mensuarius sit de London usque Lachenlade nisi dicti mensuarii et bushelli de Ripa Reginae.” V LONDON AND THE LOWER THAMES IN WARFARE The last historical aspect in which we must consider the River of London is the military aspect; and this aspect has three clearly marked divisions. We have first to consider the Lower Thames as an avenue of invasion; next as an obstacle to invasion of the northern part of the island, or to the passage of the troops from the north to the south. Thirdly, we must estimate what effect upon the military history of the country London itself has had, commanding as it does the lowest crossing of the Thames, always forming a vast base of supply, and for centuries by its stores and munitions forming an ally or an enemy of capital importance to whichever party it supported so long as warfare was waged in England.