Stewart began writing music for the piano at an early age. Taking up viola and oboe in his teens, he later went to the University College of North Wales (Bangor) where he studied composition with, among others, William Matthias and Reginald Smith Brindle. Gaining a B. Mus. (hons) degree in 1960, he returned to his old school in Rochester to teach class and instrumental music. Four years later he enlisted as oboist to the Band of HM Coldstream Guards, which opened many doors including performances of his compositions and arrangements in many national venues, on disc and broadcast by the BBC on Radios 2 & 3.
His years at Bangor had enabled him to fulfil a childhood dream of learning the harp, which he was later able to develop when he left the army and moved with his wife, Sue, and young family to Lowestoft as a peripatetic woodwind tutor for Suffolk County Music Service. His Flights of Fancy is on the Trinity College harp examination syllabus, while the Spartan Press publication Saxofun is on Suffolk's own exam syllabus. Since 1999 Stewart has been Senior Woodwind Tutor for Suffolk, and, since 2002, harp tutor as well! 2002 also saw the wedding of his daughter, Hilary, and the first performance of his Horn Concerto (written as a 21st birthday present for his son, Oliver).
Stewart's recent publications She'll be Comin' `Round the Mountain was written for the North Suffolk String Orchestra as was Haunted House. Spookily, this received its first performance at Lowestoft accompanied by a July thunderstorm!