It is not, therefore, because the crossing at London is unique--it is, on the contrary, but the last of a long series of crossings--it is because it is the _lowest_ crossing of the Thames that it came to be of such capital importance in the history of this island. Upon it converge the great military road from Chichester and the Great Port, the still more important road from the Kentish ports, and in particular from the Straits of Dover, the road from Shoreham going directly northward, of which such slight but such conclusive evidence has been discovered. These from the south--while from the north the great eastern road from Colchester and the corn-lands of Essex, the northern road with its branches to the ports and to the corn-lands of East Anglia, the north-western road from the garrison at Chester with its branch to the arable lands of Lancashire, past the fortress of Manchester, and even the western road from Bath and from the mines of the Mendip and from the garrison of Caerleon, all converge. Once this scheme of ways had been established (and they were certainly all complete before the end of the fourth century), once London had thus become the hub of a wheel of such spokes and the centre of such a web, the Thames which had made it, making also its commerce from the sea and its value as a point of transhipment between inland and sea-borne traffic, assured its eminence over all the other towns of the island. I will not here repeat the arguments which I have dealt with in other studies, and which are advanced in defence of various hypothetical dates for the first building of the bridge. Its establishment across the river marked, of course, the completion of the process whereby London was produced. For once the bridge was there it was a necessary terminal to sea-borne traffic, and a convenient one to inland traffic; it was the military communication between north and south, and the commercial one as well. I will close by distinguishing between the very few pieces of actual evidence and the presumption built upon them.