King John, needing to supply a war across the English Channel, had in 1203 ordered all shipyards (including inland ports such as Gloucester) in England to provide at least one ship, with places such as the newly built Portsmouth being responsible for several.

He makes Portsmouth the new home of the navy. (The Anglo-Saxon kings, such as Edward the Confessor, had royal harbors constructed on the south coast at Sandwich, and most importantly, Hastings.)

He has forty-five large galleys available to him by the end of 1204, and from this point on an average of four new ones every year.

He also creates an Admiralty of four admirals, responsible for various parts of the new navy.

Major improvements will be made during John's reign in ship design, including the addition of sails and removable forecastles.

He also creates the first big transport ships, called buisses.

John is sometimes credited with the founding of the modern Royal Navy.

What is known about this navy comes from the Pipe Rolls, since these achievements are ignored by the chroniclers and early historians.