William had been working to bring the autonomous cities under royal ownership, outlawing parliaments and city halls, and sending officials to manage and collect taxes directly.

However, there are a few special port cities that are exceptions, not only granted by William the right to act in the ports in a unified manner, but also given autonomy and special status different from other cities, and the autonomous alliance formed by these port cities is the Five Ports Alliance.

The Five Harbours League was an autonomous alliance of several port cities along the coast of southeastern Kent and Sussex in English history from the 11th to the 16th centuries.

The first five harbors to serve as a core included Hastings, Romney, Hayes, Dover, and Sandwich, two other "ancient towns" of Rai and Winchilsey, and 8-23 "limb" villages and towns. Although the number of ports in the alliance is more than five, the name of the Five Ports Alliance has continued.

The exact origin of the 5-Hong Kong Alliance has been debated by academic circles and has not yet been conclusive. Some historians believe that the League of the Five Cities was formalized in 1066 under a deprecated pardon and was in existence before the Norman Conquest, while others believe that it did not exist until the 13th century.

In the 11th century, the herring industry was an important economic pillar for the south-east coast of England, and fishermen from Kent often went to Great Yarmouth in Norfolk to dry their nets and salt, later known as the Don and Strond concessions, after catching herring in the North Sea.

Over time, the herring bazaar was formed in the place where the nets were dried and the fish were salted in Yarmouth, where the post-flood harvest was sold every September. The market was one of the important fishing bazaars in Western Europe at the time, attracting a large number of merchants from London, France, and the Flemish region.

In the process of competing for jurisdiction over the bazaar, the people of the Five Hong Kong and the local fishermen gradually spontaneously organized management and arbitration, which may have been the prototype of the Five Hong Kong Alliance.

In the Middle Ages, England was often harassed from across the North Sea and the English Channel, and the king of England levied "Danish gold" on the whole country in exchange for peace and the maintenance of a dedicated navy.

This policy was untenable during the 11th-century Edward the Confessor, who chose the five southeastern ports to provide coastal defense for England, and the people of the five ports provided coastal defense services for the crown in exchange for urban privileges.

In the 12th century, when the Shepwe Court was established and granted unified jurisdiction over the ports, the five ports began to enter English history as a whole, and by the 13th century, the alliance and autonomy of the Five Ports as a whole gradually matured.

The core ports and ancient towns bear heavy transportation tasks, and at the same time, they also need to help the adjacent "limb" villages and towns. If these villages and towns are assigned insufficient military service and ships, the core ports are to make up for them.

At its peak, there were 23 "limb" villages and towns, from Seaford to Breitlingsey in Essex.

The ancient towns of Rai and Winchilsey were originally the "limbs" of Hastings, but due to the silting up of the port of Hastings, the help and support of the two ancient towns were needed, and eventually Rai and Winchilsey were given the same status as the five first ports.

At the beginning of the annual herring fair, the Greater Yarmouth area receives bailiffs appointed by the Five Ports Alliance to maintain order and law. The League sent governance officials to Yarmouth and had pricing power over herring and tariffs on ships traveling to and from trade.

This tradition lasted until the 17th century and became one of the reasons for the disagreement between the local Norfolk fishermen and the people of Wugang.

During the Plantagenet Dynasty, the Five Ports Alliance was strongly supported by the royal power due to its important strategic position.

In return for his duties in coastal defense, Henry II exempted the five ports from taxes and tolls throughout England, and granted them the right of self-government to collect tolls, and to administer criminal and civil jurisdiction.

The Shepway Court is the earliest arbitral institution of the Five Hong Kong Alliance, established in 1150, and the court is presided over by the Governor of the Five Hong Kongs. This institution also served as a two-way intermediary between the king and the people of the five ports, conveying the king's orders to the people of the five ports and acting on behalf of the people of the five ports to the king, a function that was later inherited by the court established in Dover. After the 16th century, the main function of the Shepwe court became the place where the Governor of the Five Ports was sworn in.

Because of the magnitude of these privileges and the looser regulation of them, smuggling became prevalent in the region. As a result of the independence of tariffs, the trade in wool exports and wine imports was very profitable for the allied ports.

In 1215, the Five Ports League and London were written into the Magna Carta as representatives of the cities of England, and the privileges of the League were legally affirmed and guaranteed.

According to a pardon issued by Henry II in 1155, the five ports as a whole were required to provide the king and his army with 15 days of forced labor each year on 20 ships, each of which consisted of 21 seamen and one boy. These vessels are to be maintained in peacetime and used for naval warfare or cross-strait military transport during their service.

The Book of the Doom of the Port, compiled by the crown in the 13th century, increased the number to 57 ships and 24 seamen per ship. The tonnage of sailing ships gradually increased during the time of Edward III, and the number of seafarers increased to 34 people. The League's maritime power was greatly expanded, becoming not only the backbone of England's southeastern coastal defense, but also a formidable force in Western Europe.

In the 13th century, the Five Ports Alliance received a unified flag and emblem from the royal family, and the fleet of the Five Ports Alliance was awarded the title of "Five Ports Royal Navy". The king appointed the Supreme Commander and four lieutenants to control the fleet, but at the same time independent of the other fleets and not under the command of the marshal.

In 1147, the Five Ports Fleet went south to support the Portuguese against the Moors, and was highly praised by King Alfonso of Portugal.

In 1208 and 1216, England avoided another conquest from the continent by repelling the invasions of France, Flemish, and Holy Rome.

The Five Ports Fleet was praised and thanked by the king and nobles, and it was decided that all future armistice agreements between England and the outside world would be sent to the Five Ports Alliance for comments.

During the reign of Edward I, the Confederate fleet took an active part in the king's conquest of Scotland and Wales. The reputation and power of the Alliance is in full swing.

In contrast to its reputation for excellence at kings and court councils, the Five Ports Alliance was seen as arrogant in the eyes of ports and coasts on both sides of the English Channel, and was notorious for its piracy.

In 1242, at the instigation of Henry III, Confederate ships sacked the coasts of France, Brittany and Normandy.

The plundering of Gascony merchant ships in 1314-1315 can be said to be the culmination of later English privateering.

In 1321 the sailors of Winchilsey sacked Southampton, burning 17 ships in the city, and the League demanded that ships from other ports of England show their respect for the League when they pass through its seven ports, or face severe punishment.

After the 14th century, the League of Five Ports lost its monopoly and by the eve of the invasion of the Spanish Armada in 1588, its role had ceased to be relevant.

At the end of the Middle Ages, due to the silting of the harbor and the competition of other ports, the alliance gradually declined, and now only Dover is still an important port, and in 1855 most of the privileges of each port were abolished, and only the jurisdiction of the maritime court was retained, and the supreme governor of the Five Ports Alliance was the harbour master who was also the governor of Dover Castle, and the station was Walmer Castle.