Henry III was somewhat shy in disposition, but very determined. He was born in Liverpool and attended the Liverpool Collegiate School before coming down to London with his father after the death of Henry I. He completed his apprenticeship with the company in 1910 with his work on the organ for the Lady Chapel of Liverpool Cathedral, which he set out, supervised, scaled, voiced and finished. That same year, his father made him a partner and gradually Henry III assumed more responsibility until 1912 when his father retired. His first responsibility was the completion of the design for the main organ of Liverpool Cathedral and the supervision of its construction. During this period, the works moved from Homerton in East London to the Lewis Works in Brixton.
Between the two World Wars, Henry III made considerable changes to the actions and tonal pallette of Willis organs following his travels in Europe and the USA during the 1920s. Nevertheless, he maintained the fundamental Willis tonal system and method, enhanced with new and rediscovered ranks such as keen strings and mutations.
Henry III was much respected by organ builders both here and abroad. In 1916, he was one of the original executive members of the Federation of Master Organ Builders and in 1949, he was the founding President of the Incorporated Society of Organ Builders. In 1957, he was elected the first President of the International Society of Organbuilders. He was also, in 1926, the first President of the Organ Club and, in his time, Master of the Worshipful Company of Musicians.