EWIAS, Herefordshire (Fig. 17).--The brief notice of this castle in Domesday Book throws some light on the general theory of castle-building in England.[436] William FitzOsbern, as the king's vicegerent, rebuilt this march castle, and committed it to the keeping of another Norman noble, and the king confirmed the arrangement. But in theory the castle would always be the king's. This is the only case in the Survey where we hear of a castle being _rebuilt_ by the Normans. We naturally look to one of King Edward's Norman favourites as the first founder, for they alone are said by history to have built castles on the Welsh marches before the Conquest. Dr Round conjectures that Ewias was the "Pentecost's castle" spoken of in the (Peterborough) _Anglo-Saxon Chronicle_ in 1052.[437] No masonry is now to be seen on the motte at Ewias, but Mr Clark states that the outline of a circular or polygonal shell keep is shown by a trench out of which the foundations have been removed. The bailey is roughly of half-moon shape and the mound oval. The whole area of the castle, including the motte and banks, is 2-1/3 acres. EXETER.--This castle is not mentioned in Domesday Book, but Ordericus tells us that William _chose_ a site for the castle within the walls, and left Baldwin de Molis, son of Count Gilbert, and other distinguished knights, to finish the work, and remain as a garrison.[438] In spite of this clear indication that the castle was a new thing, it has been obstinately held that it only occupied the site of some former castle, Roman or Saxon.[439] Exeter, of course, was a Roman castrum, and its walls had been restored by Athelstan. In this case William placed his castle inside instead of outside the city walls, because, owing to the natural situation of Exeter, he found in the north-west corner a site which commanded the whole city. Although Domesday Book is silent about the castle, it tells us that forty-eight houses in Exeter had been destroyed since William came to England,[440] and Freeman remarks that "we may assume that these houses were destroyed to make room for the castle, though it is not expressly said that they were."[441]