north of the city, which could be seen in the distance from the high ground hard by. According to Orderic, William, after his coronation at Westminster, spent some days at Berkhampstead, during which "some fortifications were completed in the city for a defence against any outbreaks by its fierce and numerous population."[7] Meagre in details as is the history of this early period, it would appear from the foregoing passage that William caused two castles to be erected, one at either end of the city, hard by the river bank, the western one becoming the castle of that Ralph Baynard who gave his name to it and to the ward; the eastern one (after the building of its stone keep) receiving the appellation of the Tower of London. When erected on new sites, the early castles seem to have consisted of a bailey, or court, enclosed by wooden palisades, and a lofty circular mound, having its apex crowned by a wooden tower dwelling, also within a stockade, the whole enclosed by a ditch common to both; but though nothing remains of these early castles in London, it seems probable that the mound was dispensed with, and that the angle of the wall was utilized to form a bailey, the side open to the city being closed by a ditch and bank, crowned by stout palisades of timber, while the Roman wall would be broken through where the ditch abutted upon it at either end, the whole bearing a strong resemblance (allowing for the difference in the site) to the castle of Exeter. Orderic goes on to say that William at once built a strong castle at Winchester, to the possession of which he evidently attached greater importance than that of London, where the great stone keep was probably not even commenced till quite a decade later, though Pommeraye, in a note to his edition of _Orderic_, tells us "that it was built upon the same plan as the old Tower of Rouen, now destroyed." The advantages of the site selected for the Tower were considerable, the utilization of the existing Roman wall to form two sides of its bailey, its ditch isolating it from the city, while it was so placed on the river as to command the approach to the Saxon trade harbour at the mouth of the Wallbrook, then literally the port of London, and with easy access to the open country should a retreat become necessary.