A tendency therefore arises, more or less early according to local circumstance, to establish a fortified base within striking distance of the civilian centre which it is proposed to command; and striking distance is a day’s march.  The strict alliance between Paris and the Crown forbade such an experiment to the Capetian Monarchy, but, even in that case, the truth of the general military proposition involved is proved by the power which Montlhery possessed until the middle of the twelfth century of doing mischief to Paris.  In the case of London, and of a population the wealthier of whom were probably for some years hostile to the Conqueror, the immediate necessity for an exterior base presented itself, and though the distance from London was indeed considerable, Windsor, under the circumstances of that moment, proved the most suitable point at which to establish the fortress.

Some centuries earlier or later the exact point for fortification would have lain at Staines, and Windsor may be properly regarded as a sort of second best to Staines.

The great Roman roads continued until the twelfth century to be the main highways of the barbaric and mediaeval armies.  We know, for instance, from a charter of Westminster’s, that Oxford Street was called, in the last years of the Saxon Dynasty, “Via Militaria,” and it was this road which was still in its continuation the marching road upon London from the south and west:  from Winchester, which was still in a fashion the capital of England and the seat of the Treasury.  Now Staines marks the spot where this road crossed the river.  It was a “nodal point,” commanding at once the main approach to London by land and the main approach by water.

But there is more than this in favour of Staines.  I have already said that a fortress commanding a civilian population—­an ancient fortress, at least—­can do so with the best effect at the distance of an easy march.  Now Staines is not seventeen miles from Tyburn, and a good road all the way:  Windsor is over twenty, and for the last miles there was no good, hard road in the time of its foundation.

But, though Staines had all these advantages, it was rejected from a lack of position.  Position was still of first importance, and remained so till the seventeenth century.  The new Castle, like so many hundred others built by the genius of the same race, must stand on a steep hill even if the choice of such a site involved a long, instead of a reasonable, day’s march.  Windsor alone offered that opportunity, and, standing isolated upon the chalk, beyond the tide, accessible by water and by road, became to London what, a hundred years later, Chateau Gaillard was to become for a brief space to Rouen.