There is no official patron saint of the British Marines.
Major
He was captain of the British Royal Marines
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Lt Colonel
Lieutenant-Colonel.
Major is the higher rank.
The Royal Marines are part of the Royal Navy and nothing to do with the Army.
The British Commonwealth term refers to the average British citizen. The commonwealth is a term for the average citizen, the other basic level of citizenship is royal.
I believe the United States Marine Corp were formed during the the American Revolutionary War to combat the British, in particular the British Royal Marines.
Royal Marines Division ended in 1943.
Royal Marines Division was created in 1940.