Complex sentence: Sergeant Major Instructor (SMI) is an appointment held by Warrant Officers Class 1 in the British Army Small Arms School Corps and Army Physical Training Corps and by some WO1s in the Royal Engineers.
Split into simpler sentences: Sergeant Major Instructor (SMI) is an appointment held by Warrant Officers Class 1 in the British Army. This is an apoinment held in the British Army by Warrant Officers Class 1 in the Small Arms School Corps and the Army Physical Training Corps and by some WO1s in the Royal Engineers.