Admiral of the Blue

Admiral is a senior rank of the Royal Navy of the United Kingdom, which equates to the NATO rank code OF-9, outranked only by the rank admiral of the fleet. Royal Navy officers holding the ranks of rear admiral, vice admiral and admiral of the fleet are sometimes considered generically to be admirals. The rank of admiral is currently the highest rank to which an officer in the Royal Navy can be promoted (Admiral of the Fleet being in abeyance).

King Edward I of England appointed the first English admiral in 1297 when he named William de Laybourne “Admiral of the sea of the King of England”. The rank of admiral should not be confused with the office of Admiral of England or Lord High Admiral, which was an office held by the person with overall responsibility for the Navy (though usually only in title, the Lord High Admiral is typically an honorary appointment for members of the royal family).

The Royal Navy has had vice and rear admirals since at least the 16th century. When in command of the fleet, the admiral would be in either the lead or the middle portion of the fleet. When the admiral commanded from the middle portion of the fleet his deputy, the vice admiral, would be in the leading portion or van. Below him was another admiral at the rear of the fleet, called rear admiral.

In Elizabethan times the fleet grew large enough to be organised into squadrons. The squadron’s admiral wore a red ensign, the vice admirals white, and the rear admirals blue. As the squadrons grew, each was eventually commanded by an admiral (with vice admirals and rear admirals commanding sections) and the official ranks became admiral of the white, etc.

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Wikipedia