What musical instrument do you play

My school was a Secondary School we had quite a few interested in music some of the pupils became professional musicians..
Our Headmaster was a Major in the Royal Artillery.
He was very tall and used to prowl the corridors at break time looking for those who tried to stay inside in the warm. If you ran he would shout "Stop!" up his sleeve he kept a cane.
In one move he would produce it make you hold out your hand and give you a whack.
However we liked him as he controlled the rougher kids and made the school a better place.