 East Tilbury, which stands at the western end of the section of the Thames known as Lower Hope Reach, was fortified long before the building of Coalhouse Fort due to its vulnerability to seaborne attackers.Settlements on both sides of the Thames were raided by the French in 1379 during the second phase of the Hundred Years' War.The attack prompted the building of Cooling Castle on Kent's Hoo Peninsula between 1380 and 1385 but there was initially no corresponding move to improve the defences of East Tilbury.