 Only a small fragment of an outer gatehouse remains.At the time of the Norman Conquest in 1066, Plymouth, then known as "Sutton", was too small a settlement to warrant fortification, but a motte and bailey castle was built at nearby Plympton.As the value of the natural harbour, Sutton Pool, and the size of the town increased, so in 1377, a murage grant was received to fund its fortification.