Duncan McColl was a member of the International Association of Precision Therapists and the International Society for Professional Hypnosis (USA) and was a biofeedback, behavioural and management science consultant. He served as a pilot in the RAF during the Second World War. He later qualified as a chartered accountant and worked as a senior financial and marketing executive in leading British and American companies whilst spending thirty-five years abroad, mainly in the United States, Canada, Australia, Mexico and Spain. He successfully applied ancient and modern teachings, many of them not available in English, to health and business problems, to stress management, creative thinking, psychometric interviewing, and to staff motivation and development. He had an especially delightful and infectious sense of humour.

"Duncan McColl has provided us with a fresh look at how we do our work. It is insightful and provocative. It is scholarly yet remarkably free from the lanuage which constantly calls out for the use of a dictionary. It is fresh and invigorating." The Hypnotherapist.