In addition to the leading role he played in various professional organizations that served to protect doctors and the general public, each from the other, Horsley attempted unsuccessfully to reform certain aspects of the Royal College of Surgeons and then assumed an important role in reforming and leading the British Medical Association, ensuring that it became more representative of the profession and more concerned with the welfare of its members. He enjoyed being in the public eye, having his views heard, and influencing the course of events in accord with his liberal principles. He used his position in the association to support legislation to improve the health and welfare of children and then became an ardent advocate of the National Insurance Bill, which caused him to be cast aside by many of his friends. An idealistic man of strong opinions who was always ready to help those less fortunate than himself, his support of social legislation was not for personal gain. Indeed, it cost him dear, for his private practice withered as colleagues stopped referring patients to him, either in anger or in the belief that he was turning from a clinical to a political career.