To judge from the material evidence afforded by an inspection of the works, it would appear that the castle represents the Saxon or Danish earthwork, probably the earliest strong place, and was composed of a truncated mound, its circular ditch, and a bank of earth encircling an area, of which the mound or a moiety of it made part: the whole forming a burh of the first class.
The Normans, probably in the reign of Henry I., enclosed the castle and town in a rectangular wall, and dug the east and north ditches. Also the castle was enclosed with a wall built in part on arches, and a shell keep placed on the flat summit of the mound. The wall of the castle, and much of the west wall of the town, and the two houses in Blue Anchor-lane, may be attributed to this period.
Then it became necessary to strengthen the town wall, and this was probably done in the reign of King John, who, it appears, remitted to the citizens £200 out of their fee-farm rents for the enclosure of their town and the thickening of the wall, and perhaps the west and spur gates were begun at that time.
Much must have been done to the fortifications during the reign of Henry III. or Edward I. To this date are probably due the older drum towers and much of the wall connected with them, and the recessing of the Bargate and the addition of its flanking towers.
It appears that the town was attacked by pirates and sacked in October, 1338, 12 Edward III., and in consequence it was strengthened in the next year. The south and east gates may have been of this date, and the spur tower and its gallery, unless this latter be, with the completion of the Bargate, the work of Richard II. This king seems to have done much to the castle.
The vault indicated on the plan as on the north side of the water-gate is at present wholly underground, being built against and within the exterior wall, its floor being about the level of the footing of the wall. The vault measures 55 feet 3 inches north and south, by 19 feet 6 inches east and west, and is about 25 feet high. Sir H. Englefield says it has much the air of a chapel. Others call it a guard-room to the water-gate. A chapel would scarcely have stood north and south, and a guard-room, especially so large a one, however necessary for a main gate, would be quite out of place beside a mere postern. The vault was entered a few weeks ago through a long closed-up opening in the west wall, but the writer has been unable to learn what was then observed.
To the south of the water-gate is, or was, a similar vault, indicated by the openings in the wall, one 3 feet and one 1 foot from the ground, both long since built up. Probably these two were the substructures of two buildings which formed a part of the exterior wall, and were used for stores or cellars.
It is difficult to speak too highly of the large scale plan of Southampton executed under Sir H. James, upon which the lines of the old wall, and position of other objects of antiquity, are shown in a manner which leaves nothing to be desired.