see
in the Bayeux tapestry the followers of William the Conqueror in the
act of erecting some such tower of defence. Such structures were
somewhat easily erected, and did not require a long period for their
construction. Hence they were very useful for the holding of a
conquered country. Sometimes advantage was taken of the works that the
Romans had left. The Normans made use of the old stone walls built by
the earliest conquerors of Britain. Thus we find at Pevensey a Norman
fortress born within the ancient fortress reared by the Romans to
protect that portion of the southern coast from the attacks of the
northern pirates. Porchester Keep rose in the time of the first Henry
at the north-west angle of the Roman fort. William I erected his
castle at Colchester on the site of the Roman _castrum_. The old Roman
wall of London was used by the Conqueror for the eastern defence of
his Tower that he erected to keep in awe the citizens of the
metropolis, and at Lincoln and Colchester the works of the first
conquerors of Britain were eagerly utilized by him.

One of the most important Roman castles in the country is Burgh
Castle, in North Suffolk, with its grand and noble walls. The late Mr.
G.E. Fox thus described the ruins:--

"According to the plan on the Ordnance Survey map, the walls
enclose a quadrangular area roughly 640 feet long by 413 wide, the
walls being 9 feet thick with a foundation 12 feet in width. The
angles of the station are rounded. The eastern wall is
strengthened by four solid bastions, one standing against each of
the rounded angles, the other two intermediate, and the north and
south sides have one each, neither of them being in the centre of
the side, but rather west of it. The quaggy ground between the
camp and the stream would be an excellent defence against sudden
attack."

[Illustration: Burgh Castle]

Burgh Castle, according to the late Canon Raven, was the Roman station
_Gariannonum_ of the _Notitia Imperii_. Its walls are built of
flint-rubble concrete, and there are lacing courses of tiles. There
is no wall on the west, and Canon Raven used to contend that one
existed there but has been destroyed. But this conjecture seems
improbable. That side was probably defended by the sea, which has
considerably receded. Two gates remain, the principal one being the
east gate, commanded by towers a hundred feet high; while the north is
a postern-gate about five feet wide. The Roman