Over the course of a playing career that spanned roughly fifty years, John Mahon (pronounced M’hone) introduced and popularized the clarinet as a solo and chamber instrument throughout Britain. He performed extensively in London and in many provincial towns. This article presents biographies of John and William Mahon, illustrations of contemporary clarinets and a basset horn, Mahon as a teacher, his music, and his influence and legacy. William Mahon’s concerts and reviews and a conclusion end the article