A permanent staff instructor (PSI) is a warrant officer class 2 (WO2), or senior non-commissioned officer (sergeant, staff sergeant or colour sergeant), of the Regular British Army who has been selected to instruct Army Reserve soldiers.
A normal rifle company in a Regular Army battalion has a single WO2, serving in the role of company sergeant major (CSM).
The PSI is meant to provide the reserve company with the benefit of his professional experience, as well as to ensure that the training and operation of the company adheres to the Army's methods and standards.
[3] The PSI is typically responsible for much of the company's administration work, and usually takes a particular role in the training of junior NCOs (corporals and lance-corporals, and equivalent).
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