Fordwich has been formally involved in the Cinque Ports since the 13th century through its geographical and institutional link with Sandwich, one of the five or "cinque" ports which provided ships and men for the King. The original five were Hastings, Romney, Hythe, Dover and Sandwich. Later Rye and Winchelsea were added to the Confederation.

The fore-runners of the Cinque Ports first came together informally, during the 11th Century, to regulate the annual herring-fair at Yarmouth, on the Norfolk coast. From 1051, King Edward the Confessor (1042-1066) set about replacing the Saxon mercenary fleet with one drawn from the five ports. In return for tax and trading privileges, Edward was able to muster a fleet to maintain the sea-lanes and to protect his kingdom from attack.

Under the system of ship service, the Ports were required to supply 57 ships, each with a crew of 21 men and a boy (known as a gromet), for 15 days every year. In return, the Ports were granted rights which included:
Exemption from tax and tolls; self-government; permission to levy tolls, punish those who shed blood or flee justice, punish minor offences, detain and execute criminals both inside and outside the port's jurisdiction, and punish breaches of the peace; and possession of lost goods that remain unclaimed after a year, flotsam and jetsam.
These were substantial privileges, but ship service was onerous, and the five original head ports enlisted the help of neighbouring towns and villages, known as members or limbs.

Fordwich is one of the three limbs of Sandwich, the others being Brightlingsea on the Essex coast, and Sarre, on the Stour below Fordwich. The connection with Sandwich was a natural one, as cargo destined for Fordwich had to pass through Sandwich. But the formalisation of the Cinque Ports' status and privileges made it important that Fordwich should also participate.

Although the documentary evidence is patchy, it seems that Fordwich owed ship service to Sandwich during the reign of Edward the Confessor. Some historians believe that Fordwich was a limb or member of Sandwich before the Conquest, and that this membership lapsed between 1066 and the early 13th century.

The Fordwich custumal - the written account of the rights and powers of the town - dates from this latter period, and borrows some of its language from the Sandwich custumal.

In the early days of the Cinque Ports - when the Wantsum Channel was open and the mouth of the Stour was only four or five miles away - it is likely that Fordwich participated directly in the naval service to the King. At least it did so to the extent of sending seamen and helping to pay the costs of the fleet. As late as 1373, a ship shed was built on the river bank at Fordwich to over-winter a warship. But later the obligation was paid entirely in coin known as ship-money.

In the 21st century Fordwich maintains its allegiance to Sandwich and the Cinque Ports. The Mayor of Fordwich also serves as Mayor Deputy to the Mayor of Sandwich, and swears loyalty to him every July in a ceremony held at the Sandwich Guildhall. He also pays 3 shillings and fourpence (16.7 p) in ship money, and makes a speech reflecting on the towns' shared heritage.

The Mayor Deputy also attends events at Brightlingsea, Sandwich's limb in the Essex marshes, famous for oysters and sprats. These events include the annual Choosing Day in June and the Mayoral election in December, both colourful and convivial occasions.

Fordwich's own Civic Service in November, though not specifically a Cinque Ports event, is attended by the Mayors and civic representatives of Sandwich, Brightlingsea and other Cinque Ports Towns, and is our way of repaying hospitality and friendship.