Thanks Rod, very interesting.

My curiosity arise from the British officers on the Portuguese service when writing their reports in English use the expression «the sergeant major X distinguished» when they want to mention a Portuguese adjutant sergeant (the duty of this sergeants was very clear, they have to support the regimental adjutant officer in his duties). In battle the adjutant officer (a Ensign or a Lieutenant most of the times) was used many times as an aide of the commander of the battalion/regiment and the adjutant sergeant helped him, distributing orders, keeping the line etc. This sergeants were selected among the most able and not by seniority.
I suspect that in the British army there wasn't a totally equal rank/appointment so they eventually use sergeant major as the closest.

Moisés