The post holder was chiefly responsible for the command of the English navy's Narrow Seas Squadron [2] also known as the Eastern Squadron [3] that operated in the two seas which lay between England and Kingdom of France (the English Channel particularly the Straits of Dover) and England and the Spanish Netherlands later the Dutch Republic (the southern North Sea) from 1412 to 1688.

[4] His subordinate units, establishments, and staff were sometimes informally known as the Command of the Narrow Seas.

[6] In the fifteenth, sixteenth and seventeenth centuries, the Kingdom of England claimed sovereignty over certain bodies of water close to the British Isles: those between the Kingdom of France and England (the English Channel particularly the Straits of Dover) and the Spanish Netherlands later the Dutch Republic and England (the southern North Sea).

As a result of England's claim of these territorial waters there was an enforceable requirement placed on any foreign ships passing through the area to acknowledge all English warships.

Claims to the narrow seas lasted until the United Kingdom of Great Britain and Ireland, along with other European countries, agreed to set a new three-mile limit in 1822.